Simplest is a set of bar-end shifters, any old ones and simply select friction. The amount of pull per click in 7s is sufficiently big that it generally shifts cleanly.
I had forgotten about the Tourney ones. The Claris 8s are reportedly pretty good, although triples are rare.
A full Campag 8s shifter andrear mech will work fine too, the cog spacing on Campag 8 is identical to Shimano 7.
Another alternative is Campag 9s (pre-2001), and run a hubbub-cable routing Shimano rear mech. (If you don't understand what I am going on about have a Google of 'shimergo') or look at the Cycling UK Shimergo pages.