Slightly depends on what size chainrings you'll be using, and what clearance they need on the chainstay. Might end up being an 'estimate, buy a couple, sell on the ones you don't need' situation.
Yes, it´s probably too many "depends" to make a calculated buy. :)
Ended up ordering a Shimano 122mm wide one at Amazon for pennies, should fit for sure and could always get a narrower one when (if) it gets crusty.
Slightly depends on what size chainrings you'll be using, and what clearance they need on the chainstay. Might end up being an 'estimate, buy a couple, sell on the ones you don't need' situation.