Lumintop Tool Ti Mod

I have a question . A friend wants me to Mod his Lumintop Copper Tool. Is there a diy driver like the one in this flashlight ( available?
One that can work with 1,5V up to 4,2. Sure i can use a FET driver but with only 350mA from the Efest 10440 the runtime is not worth talking about. So i would prefer something with 600-700mA max for ~300 lumen out of a GP-G3 S5. And if it is only one for 4,2V it would also be ok.
Thinking about the Copper Tool i could not stop thinking about my loved EDC Tool Ti. But i would only mod it to 10440 if it is possible to stil use the E-Switch. Hope someone here has more information what is possible.