The top 2 guns as far as accuracy goes are the RAC Props version which is cast directly from actual gun parts, and the Tomenosuke Pro versions. Both are going to cost near the grand price, be it kit or finished version. Both are very limited and mostly sold out except for in the hands of resellers like Monsters in motion and ebay, but Coyle does do small runs once in a while on propsummit. Also you can find both occasionally from people that need to fund other props or family events in the prop shops here and on propsummit for less than the resellers if you check regularly. Sidkit made a decent metal kit based mostly off of RAC Props V3 gun, but he later tried to move away from Rich's work, and made new parts to make it more accurate shortly before his death. Not sure if he ever would have completely made his own gun with 100% non-Coyle parts, but that was his plan. Now one of his guys that helped him with eBay listings has control over his masters and molds and has been selling resin/metal mixed kit version in bright color resins to get past many of the new laws going after gun replicas.
Elfin Knights Project also does a decent resin kit model as well as a simple 3 part molded plastic version for around $100, but reports are that some of those came back deformed. Offworld guns can still be found and are based on 15 to 20 year old versions of the gun, but they have spent the time and money to upgrade them to be somewhat more accurate, of course at a greater price. They fall in the mid range 3-500$. Tomenosuke did an all rubber stunt version at one time for just over $100. They seem to be for people who have coveted the film used stunt versions, but are based on their regular model, and not as much the actual stunt prop. There are a few people that have sold direct resin castings from the film used stunt props, and prices can range from 100 on up with those. They have been done for many years and a lot of them are several sizes small from being too many generations away from the original. Check on threads dedicated to the stunt casts on propsummit to see the pros and cons of each. There are also toy versions currently coming out of china that could be made into a decent low quality replica for someone on a real budget, that just wants a cosplay version.
Those are the most currently available, but there have many different versions of the replica since almost right after the film came out. Some can still be found on ebay and on the prop shops one here and ebay. I myself own over 30 different version. My favorites are still the Rick Ross ones. They are still old school resin, but are true works of art and he has gone on to expand the universe with many fantasy variations on the prop that can be found on his website
http://www.pflagerkatsumata.com/ and is a sometime member here as well. It looks like his models are discontinued at the moment, but I know he is also working on new variations and may be bringing back his old versions in new forms. He also worked with Shawn Morgan to produce an official Syd Mead concept gun through Chronicle. I also know of a few 3D printed versions out there that seem to be getting better all the time.
As far as the future of these replicas go, I know there is always a desire for the most recent and most accurate model, and many people seem to still be working on them daily. With a sequel film in the works we may actually see a true officially licensed version of the gun by then. The actual film hero prop was laser scanned from what I hear, and I know licensing is something the Blade Runner Partnership said they will open up with the new film. Of course it is all Jerry Perenchio now that Bud Yorkin has passed away, and the film keeps getting delayed. So who knows?
Andy