Maybe a used scope could be more useful for you. I was also looking for these PC cards, but in the US$200 range price you won't find nothing above 20 MHz.

I bought at ebay a tektronix 2336 100MHz, dual channel.. I spent around US$350 (scope, shipping and handling to Brazil and a pair of probes)

By the way, the tektronix 2336 is a portable scope... portable like when I was young, full of energy and a scope weighing 20 lbs was portable :-)