I think there are only two cards with Mac OS 9 drivers.
One is an RME Hammerfall card with the breakout box. The breakout box requires power.
The other is the Digigram VX Pocket. I've read that the latency is bad, but never tried one.
On PPC OS X, there are also a couple of Echo Audio options - one with two stereo outs, and one with stereo i/o.
Another option is a Magma chassis with a PCI card in it. If that works for you, there are many options, up to and including ProTools systems.
If you're willing to use USB, there are more options.