Mega Man GI Joe O-Ring style

remixed from above, many of the files have been converted or simplified. Not included are the J-Hook, screws or arm pins. For the hardware I prefer using metal pieces (https://www.amazon.com/Restoration-Vintage-Action-Figures-Rings/dp/B0G8FML911)
as for the shoulders/elbows. Just use a piece of 1.75mm filament and a lighter to melt the end then use a finger nail to flatten it. Works great!

I introduced my 6 year old to Mega Man on my retroPie and now he's absolutely obsessed. This was easier than finding a reasonably priced toy on ebay.