Joined: Aug 2010
Posts: 12,760
Likes: 2,118
From: Madison, WI
Bikes: 1961 Ideor, 1966 Perfekt 3 Speed AB Hub, 1994 Bridgestone MB-6, 2006 Airnimal Joey, 2009 Thorn Sherpa, 2013 Thorn Nomad MkII, 2015 VO Pass Hunter, 2017 Lynskey Backroad, 2017 Raleigh Gran Prix, 1980s Bianchi Mixte on a trainer. Others are now gone.
I do not know what you mean by narrow chainstays.
If the frame has 135mm dropout spacing, maybe upgrade to an 8 speed wheel with cassette? I have no idea what an 8 speed shifter would go for, used probably can be gotten for a reasonable price. I think my old Bridgestone uses a 7 speed wheel with 135mm spacing.
If narrower dropout spacing, you might want to build up a wheel or have one built. Some communities have bike shops that sell used bikes, some of those shops occasionally sell used wheels too.