Depending on where you live chances are you're gonna find a common enough camo that works well enough that you can make it work. In the US, you have OCP, Multicam, UCP (which can be dyed as mentioned earlier), M81, and other miscellaneous camos that aren't as common but they can be found. The UK in particular has TONS of MTP on the market, and Canadians get nothing because its illegal to sell CADPAT to them so they buy upcharged Multicam.
The nice part about most of these is that they're good enough to make it work in most scenarios and they can often be had for fucking dirt cheap prices.
Example:
New with tags full US army uniform in OCP. Good IR compliance, comfortable and durable enough for real use, and like only 30$.
Plenty of examples out there if you look hard enough. Bitch and moan all you want about it being fed camo, but I've seen normal pairs of jeans that are more expensive than this. 30$ for a complete ready-to-use uniform is a fucking
steal.
From here, you can just modify the uniform (sewing stuff on, dyeing, whatever) and adapt it to fit your particular climate. Not convinced that this works?
Candidates in the US Army's Sniper School are expected to make their own ghillie suits using their old OCPs as a base. (bonus points for the dudes in the picture using the UCP stuff)
IR detection is also somewhat overblown depending on who you talk to. If you're in an... "airsoft game" (cough cough) where your opponents have NVGs and you don't you're fucked either way, but at the same time unless your equipment is literally glowing under IR or has no pattern under IR, you will probably be fine. Thermals are what you really need to worry about and you can't reliably get around it without the use of gimmicks or significantly adapting how you work, so for uniforms and stuff just don't overthink it.
For friendly identification in a SHTF situation there's no real guaranteed way to know if somebody is hostile or not. They could have an M81 jacket covered in kiwi farms patches that they stole from a dead guy (as unlikely as it is, but shit like this isn't likely anyways) and end up using you as a loot drop.
Also, snow camo throws IR out the window. Snow reflects all light extremely well so it's in your best interest if you glow under IR. You can get away with bright white clothing so long as it keeps you warm enough. Probably not a surprise, but I figure I'd leave that here.
Mixing camo also works pretty well in the winter, especially in snowy wooded areas.
