Hey guys

I might collect a few items from Indiana Jones, not planning to make a huge collection of it
This is a pretty much what I said before spending a ****** load of money on my Indiana Jones collection. Lucky me I wasn't quite the bttf addict you seem to be when I started my Indiana Jones collection. But lets face it, collecting Indiana Jones stuff really is a hobby that requires a strong sense of focus, money wise at least.
As for the items you want to get, here are my modest advices.
Indy's Fedora:
Penman Hats. They make what is without a single doubt the best Indy hats out there. They are quite pricey and the order process takes a long time but you will also have the chance to get a custom made fedora by one of the best hatter out there. And seriously if you need to put some money in just one prop it must be the Fedora. I mean is there anything else Indy related that is more iconic than this hat ?
Whip:
If you are on a budget, Magnoli offer the best compromise. His whips are awesome, very well crafted and well let's say close enough to the real deal. I don't think they are meant to be used too often but as a display piece it looks ace.
Diary:
There are not many options out there if you want to spend less than $300. I only have Sarednab's hero version which I am perfectly happy with (after a few alterations) so I can't really compare with others.
pocket knife:
I don't know about this one. But I'm interested in anyone as a suggestion.
gun:
I think there is an ongoing run of these on these boards. However you might face some troubles if you want to import a gun replica in the UK or you would have to compromise on accuracy and have the barrel painted in a vivid color.
Headpiece of the staff of Ra:
Go with RelicMaker's "Raven Bar" version. I personally fancy his "Imam" version better (probably because it is cast from an original headpiece) but they are not available anymore and the "Raven Bar" version is widely considered as the "hero" prop since it's the one used in the map room anyways.
Fertility Idol:
If you can get your hands either on a hata or a "hero" idol from sskunky you'll get some of the best idols ever produced (and with lineage to a screen used idol too).
I think that Sarednab has something quite impressive in the works though based on a Gobler idol (so you get something with lineage to a screen used idol as well).
Lao Che's diamond and coins:
I think Magnoli offers the portuguese coins on his website (or last time I checked he did). As for the diamond markpoon's version is sold out so maybe you can find someone to provide some measurements and get a crystal cut yourself or wait for one to pop on the secondary market (which happens from time to time).
Lao Che antidote:
Not a lot of options out there. Maybe you can try and pm Wolfie who offered them here awhile back. They are not 100% accurate but they are affordable and definitely look the part.
Sankara Stones:
Landron Artifacts for the static version. I think that Azuma is still taking people on a wait list over at COW for his 2014 run of translucent stones that actually light up.
Sanskrit manuscript:
Jedi-spirit offers a great and affordable version of these on ebay.
Voodoo doll:
I'll go with markpoon's torso as there isn't a lot of other options out there and finish the doll myself (if I had the required skills)
zalim's pin:
RelicMaker again makes the best pin. I don't know if he still offers them but you should definitely pm him.
Chalice of Kali:
As far as I know Sideshow's version seems to be fairly accurate and still widely available.
The cross of coronado:
This one is a tough one.
Sarednab has an amazing cross in the works, extremely accurate with an impressive attention to details.
However, based on pictures only, I think I still like RelicMaker's cross better. Sarednab made the cross that is possibly the closest you can think of of one of the screen used crosses but I think it looks too much like a prop in the end and less like an actual artefact. Once again it's something I get only from the pictures but RelicMaker's cross looks more like the way I always envisionned the cross. But it's only a matter of opinion since both are amazingly talented artists and offer some of the best Indy replicas ever made.
Holy Grail:
This one is quite easy, go with Restaurajones'. He makes the best grails, hands down.
Grail knight painting:
I don't own one but I think Peter74's version is one of the best ever made.
AND MAYBE, the crystal skull and the Fransisco de Orellana mask:
Who in their right minds would consider collecting anything related to "Indiana Jones and the Kingdom of that god awful unnecessary fourth movie that almost ruined one of my childhood heroes" ?
If you want to see some pictures of some of these items, you can take a look to my collection by following the url in my signature.

Good luck in your quest and try to enjoy it. Looking for the items is like half of the fun.