AGX is all but dead I think. I just checked NewEgg, the ONLY place to shop for Computer Parts, and here is what I found that might suit you. Not sure on your exact dollar range, but these are the only ones that will give you ANY kind of satisfaction for your gaming needs.
This is the "top of line" ATI AGX Video card...
Newegg.com - HIS Hightech H165GTQT512GDDAN-R Radeon X1650GT 512MB 128-bit GDDR3 AGP 8X IceQ Turbo Video Card - Desktop Graphics / Video Cards
And this is it's cheaper cousin...
Newegg.com - HIS Hightech H165PRQ512AN-R Radeon X1650PRO 512MB 128-bit GDDR2 AGP 4X/8X Video Card - Desktop Graphics / Video Cards
This is one is an Asus that is fairly decent and comes with a $20 discount and a free purchase of Worlds of Warcraft lol.
Newegg.com - ASUS AH3650 SILENT/HTDI/512M Radeon HD 3650 512MB 128-bit GDDR2 AGP 4X/8X HDCP Ready Video Card - Desktop Graphics / Video Cards
I hope that helps? As I said before, your pickins are slim. If you want more of a used selection? You can always hunt down eBay. But you get what you pay for from there. At least with NewEgg, you CAN NOT go wrong there!!
Good luck!
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