I don't know how much they cost, but Sram makes bar-end shifters compatible with their road groups...
http://www.sram.com/sram/road/category/non_series

(looked it up and the TT500 shifters are $120 on niagaracycle.com)

Could be a reasonable back-up bit of equipment to keep on hand. Unfortunately, I don't think the Sram bar end shifters have a 'friction' option like SHimano ones do.

On that note, Shimano bar end shifters would also work in friction mode, as well as Rivendell 'Silver' friction shifters, and old-school bar-cons you might be able to find on e-Pay.