Would a GeForce4 Ti 4600 do the trick?
Yes, but remember your AGP slot is 2x. You need a 2x/4x card such as the real Mac version. If you flash an 8x PC version, you'll have to do hardware mods of the card to make it work in your G4. There are threads on that in the
graphics card section.
I have a Sawtooth myself, my main machine from a decade+ ago. I've been restoring it for over a month, in theory to reach my supply of legacy games. Turns out most of them can be run on my G5, so it's proved a hobby-restore project. Still fun.
Below are Mac graphics cards with OS9 compatibility, sorted by speed. Similar-speed cards are grouped:
GeForce 4 Ti 4600 (AGP - OEM). Fastest OS9 card.
Radeon 8500 (AGP - retail), also easy to flash many PC versions.
Radeon 9000 (AGP - OEM) or Radeon 9200 (PCI - retail). They're more-or-less the same.
GeForce 3 (AGP - OEM)
Radeon 9250 (PCI - hack) was never released for Mac. Some have flashed it successfully. It's slightly slower than the 9000/9200.
Radeon 7500 (AGP - OEM) fast in OS9, slow for OSX.
GeForce 4MX (AGP - OEM)
Radeon {original} (AGP or PCI - OEM/retail)
Radeon 7000 (PCI - retail) even slower.
GeForce 2MX (AGP - OEM)
Rage 128 / Rage 128 Pro (AGP or PCI - OEM) original card the Sawtooth came with. Very slow today.
I may have missed a card or two. Someone posted a hard-to-read grid in
another thread. I don't completely agree with his/her speed order for some cards. If you want to investigate flashed PC cards, try the
Graphics section here.
Note that Radeons sometimes have trouble in OS9 with widescreen monitors connected over DVI. Where you only get standard 4:3 or 5:4 aspect ratios, and forcing widescreen ratios cause a blank screen. I'm not sure if it affects everyone, but it does affect my 1920x1200 monitor. Connecting over VGA avoids the issue - all resolutions work. OSX is unaffected, all DVI & VGA resolutions work. nVidia cards are unaffected in 9 or X.
I bought a new Firmtek SATA card, to guarantee OS9 boot. I had planned to buy one on eBay, but got tired of waiting after some weeks. They only appear now and then. One sold for under $20 about a month after I bought.