I just made a 14500-only 3 amp linear driver for the UT01 / E11. It’s a bit tedious though. Info here: What did you mod today? - #8989 by gchart
It is said that the Lumintop GT Micro driver is a drop in and you can ask at the Lumintop AliExpress store to get one. See here for more details: Utorch UT01 Mod BLF A6 Driver With NarsilMQ8 1500 lumen's - #16 by 80T