I agree with the others, other than finding a shifter that works for you there is no reason why you can't. are you handy around bikes and doing your own work? if so it may simply be a matter of modifying a clamp and using a longer bolt and nut.
I see someone recomended Brifters. however you did not mention what kind of barends you have and wether they are friction or indexing. I guess because you mentioned the thumbies everyones assumed you have shimano index shifters.
a bit more info on that plz
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk