I would suggest a bench vise. The beefier the better (but be careful not to clamp down too hard on the plastic.) One way to do it would be to use your typical woodworking clamps c-clamps, or whatever to press it against the top of a vice or a pair of blocks split enough to let the bolt/pin to fall through. the big thing is you don’t want it flying anywhere when you start applying force.

a hydraluic press would push it out with more control on such a set up, but most people generally don’t have them. that’s why I suggested the hammer-and-rod set up. what that will do is let you apply force diretly to the pin; and with it slightly undersized, it won’t replace the pin.

Generally the entire caster wheel assembly would be replaced instead of specific parts of the assembly. these kinds of wheels are not made to be taken apart to be repaired- which is why you’re having all this difficulty. amazon has plenty of kits- but try and match brand to brand.