Thanks for those links, one of them pointed me in the direction of the Shiftmate, which sounds like it will allow me to use ergo 10 speed levers with a SRAM dérailleur like an X.7 which will handle up to a 34 tooth max. I'm debating between a SRAM 9 speed 12-34 cog or an IRD 10 speed 12-34. The SRAM is <$50, the IRD is >$150 - I guess there's not much debate... A SRAM x.7 dérailleur looks like an even $100 and a shiftmate is $40. So for ~$200 I can get the low gearing I'll need for my trip without going full triple and I can use the components on a future dedicated tourer