Joe,
There are several options, among which you can find the at-mio-16xe-50, the at-mio-16de-10, at-ai-16xe-10, at-mio-16xe-10, at-mio-64e-3, and at-mio-16e-1. If you only wanted for counters, I would look at seriously the at-mio-16xe-50.
Hope this information is helpful.
L Aguila
Applications Engineer
National Instruments