What is the best place on the internet to buy accessories for gestalts or G1 transformers??

He's a teeny bit pricy, but check with Chris at Wheeljack's Lab, there's usually not much he doesn't have a ready stock of, and his customer service is excellent. I've bought a few bots from him, including a 100% complete G1 Mirage, and a few Insecticons. His site also has a comprehensive listing of every G1 TF available including mail aways, with photos and (his) prices, as well as the same for parts/accessories. Other than that, try rolling the dice on Ebay. Search for something like "transformers parts", "transformer parts", or "transformers accessories" or "pieces" and be prepared to look through photos of piles of random parts for the pieces you need. If you don't have the patience for that, try searching the name of the gestalt only, and see what comes up. Again, look for parts listings, but just search the name. Sift through the listings, because people don't always know how to list what they're selling. The trick to Ebay is to know how people might incorrectly list something if they don't know what it is. I bought a nearly mint condition G1 Swoop for about $12, because it was listed as "Transforming robotic pterydactyl toy 1980 1984 like new!!!" or something like that. (Swoop usually brings in between $100 to $150 in worse condition than the one I got, when listed properly.) Try searching for what your aunt Debbie might call the parts you need, and you may be pleasantly surprised at what you may find.