Sounds like your buddy doesn't know how to set up a derailleur.

Shimano bar-end shifters are compatible with all shimano front and rear derailleurs... as long as you have the number of sprockets for which the shifter is designed... and in some combinations it will even sorta work if you don't have the same number of sprockets...

...and there is always 'friction' mode.

Gawd I love my bar-end shifters.