I'm wondering if an Arduino with an H-bridge shield could be all the circuit you need. Plus a coil of course.
Do you have any links to discussions of pulse duration, frequency, intensity? Does it have to alternate - I.E. reverse polarity?
The fact the camera flash worked suggests that low frequency high intensity pulses work just as well.
Let me post some links that dig into PEMF… a range of things. Much beneficial research…. anything you can derive and improve on.. well... tx for coming back with a query.
http://web.orthofix.com/Products/Products/Physio-Stim/PS-1413 PEMF Brochure.pdf