@corsairpilot62 pretty much has it all, but here it is again with some extra information. No FFP/SFP on a fixed power MST-100 scope. No bipod on the A1, however, later on Wichita made some studs that replaced the front sling swivel, so a bipod could be attached. Wichita still makes these studs, just give them a call and buy one for your A1 stock if you want to run a bipod (Wichita contact information is below). M40A3/A5/A6 bipod is the Harris S-BRM 6-9" bipod with a KMW Pod-Loc.
No idea what scope would be similar to the MST-100, hopefully someone else has some information for you on that. The closest thing I can think of would be to use a SWFA 10x42 SS HD, I know that lots of guys here used them on builds in the past as a cheaper alternative. It's more like a Bausch & Lomb 10x, rather than a Unertl MST-100, but it's a good cost effective 10x replacement. That's the closest I can think of, maybe someone else will have other options for you.
As for a desert M40A1 HTG stock, I've never seen one. The closest I've ever seen to a molded in desert color HTG would be the Navy SEAL M83 stocks. However, this is more of a silhouette style with a very large cheekpiece, so it's nothing like the HTG, but it's about as close as you're going to get. Most of the M83's had Bausch & Lomb scopes on them, but I have heard of some being set-up with a Unertl MST-100, so it's similar to the M40A1 in that regard (also Remington short action, typically B prefix serial number, 7.62x51, 1 piece scope base or a 2 piece scope base, Leupold scope rings, etc.).
If you want a desert M40A1, you'll have to just paint the stock yourself. If you want a desert molded in color sniper rifle, the M83 and M86 would be great choices or you can do the M14 desert smear USMC shooting team build for a target rifle. Here's my desert smear M83 stock with some other very rare stocks like the Navy SEAL used Baker Special.
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Notice how the M83 stock is a little shorter than the rest, this is mainly due to it missing it's recoil pad (which was a much thicker type than on the M40A1 HTG stock). Most of the known M83 stocks are also in a later desert pattern, which the M86 and M14 stocks are typically known for. My M83 stock is pretty unique in the fact that it has an earlier smear pattern. Notice how it's a smear instead of a set pattern, it also has very little green in it. This is one of my favorite stocks an I'm excited to just do a custom build with it, not an M83 build (previous owner modified the stock too much, would be too difficult to do an M83, so it will just be a custom gun). Here's my M83 desert smear with 2 of my USMC desert M14 shooting team stocks and a close-up of the early smear pattern.
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I know this isn't the answer you're looking for, since you asked about a desert pattern M40A1 HTG, but as far as I know an A1 in that pattern doesn't exist or it would be a one-off civilian order that someone has squirreled away. The closest I can recommend for a factory molded in desert color would be the McMillan silhouette style M83 stock, which are also very rare.
And here's Wichita's contact information in case you want to get a sling swivel stud to mount a bipod on a McMillan HTG M40A1 stock:
@AquaRhombus77, I hope this information is helpful, please let me know if you have anymore questions.
