The Roland TR-8 drum machine is the prefect complement to the TB-03 synthesizer. In the TR-8, you can find the old school beats of the TR-808 and TR-909, plus more. There's a smooth heavy bass drum; a snare; toms; claps; hiats; and cymbals. The ride-cymbal in particular gives a nice spacey sound when used in combination with some delay, and perhaps one of the scatter effects.
There are multiple input and output options, including analog connectors, MIDI and USB. The TR-8 syncs fine over MIDI with the TR-03, as slave or master. However, I was surprised to find that connecting the USB to an old computer did not go so well; it somehow interferes with the clock, so notes are skipping, even when nothing is connecting to MIDI nor audio on the computer.
Finally, my own MIDI monitor is starting to come along, and can now understand both TB-03 and TR-8 messages, including all special controllers. The PatternHistory is already useful to see which notes and patterns are playing. So far only one instrument at a time is supported, but more is coming.