Originally Posted by 25.4TPI

I too enjoy bar end shifting. However, it sounds like you might have a secondary concern, getting a 10 speed chain stuck between rings with 3/32 spacing.

Measure the space between rings and see what comes up. Nominal outside width of a 10 speed chain is 6mm. Do the rings have spacers between them? If so, it’d be possible to get shorter chainring bolts and thinner spacers.

Also, if your current hub is set up for a smaller number of gears then a 10 speed cassette might be too wide to fit.

Are you going for more gears to have less jump between shifts or to get easier gears to climb in?

Not that you asked, but another, simpler alternative is to get a cassette with the same number of gears but a wider gearing range. Rivendell sells some 7 speed cassettes with just about whatever range of gearing your heart might desire. You just have to make sure your rear derailleur can handle the large cogs.