What format or formats are you trying to convert?
Any digital camera with analog inputs (RCA/s-video) and a firewire port will do the trick as long as you have the hardware to playback the source.
If you need to convert Hi8, you will need a Sony digital 8 to play the tapes, but you will also be able to hook playback hardware to it like a VCR if you also need to convert other formats. Just make sure the Sony Digital 8 is a model that will paly back Hi8 for Hi8 conversion...some don't - It should be listed in the specs or on the camera.
If you don't have to convert Hi8, than I would recommend any mini-DV camera.  Most have analog inputs and firewire, especially older models that can be found for cheap at pawn shops or private sellers.
Sorry I don't have model numbers for you, but the Sony DCR TRV series is a good way to go for Digital 8. Â