I am working on kitbashing several military figures along with a Joker figure and am in need of the kind of neck adapters found mostly [?] on older E&S Gen2 figure bodies similar to this one.
But with the smaller base [see image #2].
I have looked on eBay, but I am unsure if they are the right ones.
The ones on ebay are all pretty much the same aftermarket generic ones which are a clone of the most common Hot Toys one. Hot Toys sometimes has ones with different sized “bell” top halves or smaller bottom halves but they don’t get parted out separately. The only “modern” ones I have seen with a shorter base are Easy Simple’s newer heads for the slim bodies. Various figure bodies sometimes include them as spare adapters, but again are rarely ever seen parted out. I’d probably try one of the clone Hot Toys bodies that includes one as the bodies are cheap and if they don’t fit at least you have a usable body. Those clone bodies are also sold branded as Very Cool, ZY Toys, Very Hot and a few other “brands” if I recall.