If you want to keep it "stock or near stock" then why not just rebuild the rear wheel. You didn't say whether the hub or rim was shot, or both. Matrix rims are not uncommon on eBay, though the 27" ones seem to be a bit rarer than the 700C. Other similar vintage rims would be Mavic G40 or MA40 (medium-dark gray, eyeletted) or Wolber Alpine (hard to tell from the Mavics from a couple feet). If your rim is really black, then you could use the Mavic Open Pro that's a current model, I think, and fairly ubiquitous if not. You might even be able to score a Mavic non-Helicomatic rear hub that would complement your current front hub.