I just figured out that the bike that I just bought (1986 Raleigh Technium 480) has 27x7/8 tires on it that are severely dry rotted. Is there anywhere I can get new ones or am I out of luck? I really dont want to go all the way to 27x 1 1/4. Is my only option to go to 700c wheels? If so what is the cheapest way that I can do this? Estimated cost?