Is this site legit? The drop down list of sizes is showing pants with inseams of up to 38"? The color of these pants say grey. Also, I looked at a diff g-star pair of pants , and it said the model was 73.5" tall and was wearing 29x30... something sounds wrong about that
As far as your search, have you tried ebay.co.uk for the belt? I'm sure you can find it there or at least a generic black cotton web belt (they look pretty much identical). If you go to ebay.com, you can probably find international shipping for the elbow pads.
A few things that I've noticed about the pants prefixed with: 81105
1) C seems to be the version that people on here agree on.
2) However, the picture shown in the black suit gallery from post 1, and the picture you showed, shows that there is not a horizontal zipper on the right thigh (at least not in all pics)
3) C and D seem to have the same left pocket design. E has different seams for the left pocket. They all have a horizontal left zipper though
4) C and E seem to use the same material. D says to use a cross-hatch weave and probably has a different feel/look to it.
5) All 3 have different seams for the right side pocket. The zipper is only horizontal on C, and vertical/angled for D and E.
6)The pictures indicate that the darkness of the pants does not match the darkness of the shirt. "D" seems to be the least "black" out of the 3.
Are there any good pictures of the pants that show they are, in fact C and not D or E?
Update:
The following are the official g-star links to all 3. The first is the one we have as the official. The second (81105D) one is very close, though it appears to be a slightly different material (not sure how noticeable it is in person when not up close). The 3rd one (81156E) is the current one you can buy directly from g-star. The 2nd one you can find on ebay and a few websites and the first one (81105C) you may only be able to find them in dune possibly sage if you're lucky.
https://www.g-star.com/en_us/product/men/pants/21.141.81105C.5352.990
https://www.g-star.com/en_us/product/men/pants/21.142.81105D.6370.976
https://www.g-star.com/en_us/product/men/pants/21.151.81156E.5352.990
Given how current the 81156E is, I have doubts that it was used on the show.