The video ram is *NOT* upgradeable unless you have some extremely l33t soldering skills. Also, I doubt Compaq is going to sell you individual memory chips and you'd have to find out what to change (it isn't exactly going to have jumpers) in order to get the core to recognize/use the extra RAM.
Do you have any sort of proof in any form that it is not upgradeable? I'm not saying it is, but it is a possibility. You know, way back in the day, video cards had upgradeable RAM.
Also, most likely, in the 32 mb version, there are just some empty spaces where the ram would go, and you would have to solder it in. If you were to come up with the ram chips, and go to the trouble to solder them in, it would probably just work without having to change a jumper or something. I had an old PCI video card that had some removeable ram, and you pull it out and it works, reading that it has less ram. Its just like the ram is on the colmputer, you put more in, and you don't have to change anything.