I recall seeing a few new AGP cards released a few months or a year ago for PCs, but I think they will be very rare now and even more rare for Macs. The only AGP cards I see in my catalog are ultra-low-end and are for PCs only. I doubt you can get a new AGP card based on a new chip these days, especially for a Mac. AGP has almost been completely replaced by PCIe now.

Are you sure that your card is dead? Maybe its reparable or something...