Harris cyclery will sell you 27" rims, hubs in your choice of fixed, fixed/free, fixed/fixed, etc. and in various widths to fit whatever dropout space you've got. They also sell spokes and can even build the wheels for you, if you'd like.

I bought some Dia Compe centerpull brakes for my Peugeot Mixte; they'll reach the 700c wheels just fine.