I get mine (RA1 shaved) from Radial Tire in Maryland. They are a great shop and the owner is a longtime BMW racer. Talk to either Paul or Sam.
http://www.citypubdc.com/exclusive-r...ils.php?ID=788
Radial Tire Company
Silver Spring, MD
9101 Brookville Road
Silver Spring, MD 20910
PH: 301-585-2740