If you want compact, I'd suggest looking at the Barnack style rangefinders. Those from Leica and Canon are probably the safest bets. Throw a collapsible lens on and its about as small as you're going to get.
You could probably find a wonderfully serviced one for in the $300 range. Throw in a Elmar 50mm 3.5 for another $200 or a Russian copy (some of which are very good but can be hit and miss) and you've got small, rangefinder, unmetered, etc. You'd need an external finder for wider than 50mm but thats the tradeoff for the small body.
If slightly larger works, I'd suggest looking at a Canon P or Bessa.