FM2 or FM2N would be fine, second the F2 but it's quite about larger/heavier and more robust.

M3 would be great but you a) wouldn't want to use a $300-400 body without a $100-200 CLA (camera tuneup), or b) would need go over your budget at 650+ to find a user one, and that'll likely be ratty without a perfect viewfinder but mechanically ok.