I've got a NewerTech 240MHz G3 upgrade card that fits the 71xx, 81xx & 91xx PPC Nubus machines. It's not seen the inside of a machine for some time now, but last time I had one it worked fine. I also have an Apple HPV PDS card (820-0522-A, 1MB VRAM) and the requisite NewerTech video card adapter doodad that makes the HPV card work with the G3 upgrade card in the PDS slot.
If you've got a 1st generation PPC, and you've never tried a G3 upgrade on it, you're really missing out; it really transforms the old iron to something that's snappy and truly useable, not to mention much, much more stable. And if you're using the onboard video on one of these beasts, especially without the G3 upgrade, you owe it to yourself to at least try this combination.
Package deal; the accelerator, adapter bracket and video card for $25? Shipping in the lower 48 states included.
PayPal (non-credit card, please. don't like having those nasty fees deducted) or money order.