I'm able to play a .135 perfectly at "35. Judging by the sound of things, I'd say you need to get a .145 and work your way down from there. 45-60-80-105-145 off the top of my head, would give you a nice balanced set.
La Bella makes a medium balanced 4 string set that runs .110 .085 .061 (.060) .044 (.045) - see if you can find a similarly-gauged set and put a .140 or .145 underneath as suggested above
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