Any OpenHCI (OHCI) compliant USB card will work.
I got a generic one that I bought from a PC store, shoved it into my Power Macintosh 7600/132, installed the USB drivers from Apple's Web site (Or you could just re-install Mac OS 8.6+, and it will install the drivers). The card works Flawlessly.
The PCI ports in the PM 7600/132 are PCI v2.0 compliant, my USB card is PCI v2.2 compliant, but works well (And why wouldn't it?)