a. Find a _good_ genetic engineer.

b. Splice appropriate genes from electric eels into hamsters, because they're smaller and cuter and, well, hamsters.

c. Feed the hamsters.

d. Surgically install appropriate electrodes.

e. Periodically drain off the voltage.

P.S. How could I have been so blind? Splice in genes from blue-green algae as well, and you wouldn't even have to feed the hamsters! (Well, maybe some phosphorous and iron and stuff)