So here is a very simple circuit that you can use to synchronise Nanoloop (for the Nintendo Game Boy) to a MIDI clock source (such as a sequencer or a drum machine).

This circuit works and has been tested,however it is an experimental circuit and of course I can't guarantee that if you build it, it will work. At any rate, at least you won't be wasting much money because the only component that is needed is the 4017 IC, which cost me about $1.

Read the tutorial here.