For saibamens you can use the sofubi ones. the pic is the one i have that is separating from the ground. there is another one in the set that is standing, somone else posted a better photo of them next to figuarts for cell juniors you can use jakks\ irwin
my pod is irwin and they sell for an unfortunately high amount on eBay around $200 in the box. the quality is great, but I doubt figuarts Vegeta would fit inside and the door would close.
the saibaman is bandai real works and he comes with saiyan saga Gohan so you have to buy Gohan to get him. adrenaline has one for sale by himself right now though. I wouldn't recommend it though because it is too small for figuarts. the one iamreaper has is the banpresto vinyl one and it looks more appropriate.
Irwin king kai would probably work for figuarts, he's the largest king kai figure ever made to my knowledge. mine is slightly customized in that I cut off his antennas and glued them on in a different position.