Do 6 speed flight deck shifters exist? I'm interested in changing my bike from downtube to flight deck shifters, however I'm struggling to find any 6 speed flight deck shifters. I have a suspicion they don't exist.

Thanks a lot.
I've never found a 6 speed brifter, but that's no proof that they don't exist.

You might get away with using a 7 speed brifter like a Shimano RSX  on the right hand side, if your rear 6 speed cassette is a Suntour Ultra freewheel with a 5mm spacing.

"Regular" 6 speed is a spacing of 5.5mm and that adds up quickly over 6 gears to 3mm which is halfway to the next gear and won't work
Spacing crib notes from Sheldon Brown's site at https://www.sheldonbrown.com/cribsheet-spacing.html



You might choose to leave the front derailleur on a downtube shifter if you can't find the correct one for the left hand.

Downside about using a 7 speed brifter is that they are indexed, so you will have a dead or ghost click past the high gear, where the inner cable goes slack and your rear mech is held on the limit screw, which might not be quite the right position.  If that happens you just upshift once to get to the highest gear.



Your other option is to replace the rear hub, cassette, chain, perhaps the rear derailleur, and one or two brifters for something more recent.  This probably entails stretching your frame to fit a wider hub between the dropouts.

Finally  - after some searching it turns out Shimano's Flight Deck is a pair of brifters combined with a cycling computer/display, a wheel sensor, and a pedal/crank sensor.   The lowest gear count I could find was a 9 speed double and a 9 speed triple, so if you want this functionality you will need  a possibly expensive upgrade.