Thank you for using foam and actually crafting it. It's so annoying when ppl make a video on how they "made" something and all they did was 3D print it
Made something similar as a kid but with paper mache and for the elbow part I used cloth like old rag glued underneath the pieces with velcro for flexibility and adaptability with other pieces.
I sell the patterns on Etsy (merch store link in the video description) I don’t remember how many pieces it was but the foam I use either comes in packs of six or a roll that you can get at Michaels crafts.