You can build up new wheel with a pair of Sun CR18 rims (probably 27s in your case) for $27,20 @, and some spokes from eBay seller Childhood Dreams (best deal on spokes anywhere if you don't mind cut vs rolled threads).

If you can find good vintage wheels or rims locally (AND in good condition) that could be your cheapest option, but vintage wheels comparable in quality on eBay get very expensive when you consider shipping costs, and prices on better ones (Mavic Mod E's, Super Champions etc) are very high now.

Don't even consider steel wheels. Upgrading the wheels to alloy is the smartest thing you can do. - I've done it many times, and it can turn an OK bike into a GREAT bike.