Hello brad, usually may variant(s) na specifically made na trigger-type na shifter for RB. Yung last na nakita ko na ganyan is from Shimano Claris Group, tingin ko brad you need to check yung mga feature(s) na meron yung item na meron ka like yung "SIS", "XIX", etc. kase usually if same product gagawa sila ng margin of compatibility.
And the best option will be going to your LBS and consult sa mechanic para mabigyan ka din ng advise incase something is wrong or needs to be adjusted.
Less friends, less bullshit. Keep your circle small, and your beer cold.
The closest you'll see to flat-bar road bikes are folding bikes. Most upgrades to folding bikes require road bike parts primarily because MTB chainrings are too small to sufficiently drive small wheels.
For 10-speed flat-bar road bikes you'll need Shimano Tiagra 4600 or 4700 shifters. You cannot use Shimano MTB shifters due to Dyna-Sys altering the cable pull and affecting compatibility between road and mountain bike shifters and derailleurs.
Among the current groupsets, the highest groupset that supports a triple crank is Tiagra. Ultegra and 105 used to support triples back when they were 10-speed, but have done away with it.