I found two different PCMCIA cards that you might be able to shop around for a decent price on. One is the iRez Capsure that says it's Win 98 compatible on some sites, and Mac only on others.

Next is the Margi Capture-to-go. Seems pricy though.

Nogatech did make some as well, but they were bought by Zoran, and the products seemed to disappear.