Update 7/25/2018 Reddit user quicksilv3rflash just posted a DIY TMS how-to on Instructables!

Most of us are attracted to the idea of DIY tDCS because of the low entry barrier – a nine volt battery and a simple circuit (at least in theroy). But also because so much of the science literature coming out around tDCS hints at exciting possibilities for enhancing our cognitive abilities. The thought of DIY TMS, with it’s high voltages never occurred to me. I was shocked! to find these videos of DIYer Ben Krasnow on Youtube.
HatTip to Marom Bikson, this came to me by way of his Twitter @MaromBikson