Sadly with these parts being 30 years old & having always been rare & expensive on the secondary market, you’re going to find it’s much easier (and probably not much more expensive) to buy the toys again, complete.

My Nightbeat came without the seat & side guns, but I bought him accepting I’d probably never get those. I paid $5 (flea market find in around 1996) and was willing to make that compromise at that price. To he honest I won’t buy a G1 toy missing a key accessory like the *master because well... it can cost more to buy that accessory, if I can find it.

That said, best of luck!