I recently found a source for 44/48 IDF weber carb parts such as throttle linkage arms, seals, etc that are seemingly impossible to find. I broke a throttle arm at the HSR vintage race a couple of weeks ago and had an emergency weld repair done. The guys at Pierce Manifolds seem to have everything and lots of it. They are on the web at:
http://www.piercemanifolds.com/products.htm