Actual driver boot is ∅22mm like Jaxman Z1, doesn't it? You could go Kaidomain's H2-C boost driver plus XHP35 HI. Sense resistor is 1206 imperial units, 75mV sense, thus add an R100 over the stock R050 for up to 2.25A driving current. More info here: Buck and Boost Drivers, Testing, Modding, and Discussion (Pic Heavy)
Cheers ^:)