I'm heading out on a long tour soon on a bike with Shimano STI shifters. That choice was intentional as I don't like bar-ends. However, I notice the gear cables run through stops at downtube shifters bosses and I'm curious if there's a type of cheap friction shifter that would mount on those and could be used on either side that I could carry as an emergency replacement in case an STI ever crapped out.
Here is a picture of the bosses on this bike:
If someone could point to one or more specific models that would fit this, that would be great. Again, the emphasis is on cheap. If I break an STI, I would only need this to limp a day or two to the next major city (tour is in Canada). So I don't want to drop $100+ on some bespoke hand-milled stainless steel shifter.