I'm trying to find a alternative waist section for my Genoace custom, so I can use the more flexible hip joint found on most modern high grades. It doesn't necessarily matter what the alternate waist section looks like, as long as it's square-ish and isn't much larger than Genoace's current waist. I am not willing to destructively modify any parts (cut off pegs, drill holes, etc) and I am not able to create any parts due to lack of resources.

For those unfamiliar with this kit, the waist section has a cavity in which a large poly-cap ball joint can be inserted into. The usual high grade kit instead has a waist section that has a peg with a poly-cap ball joint on it.