Breezer seems to make good basic bikes, e.g.:

http://www.breezerbikes.com/bikes/details/greenway

yeah though for $300 you'll want to be looking on craigslist.

I have bought spare tires in odd sizes through

www.biketiresdirect.com

This: http://sheldonbrown.com/tire-sizing.html is a good place to start for understanding tire sizes. The old 27x1-1/4 is ETRTO 32-630. You can still get tires in that size but not so easily.