27 1/4 " rims are not made new anymore so you are looking for a dealer with old stock or more likely going to cycle jumbles to find them.
You could try 700c rims instead. The difference at the brake is only 4mm. Hopefully your brakeset will have enough adjustment left to accomodate this and the new rims will give you a much wider choice of tyres. A bit more clearance under the mudguards too if you use them.