One more thing, since you mentioned the Wein cells: there are cheap (ca. 14 Euro/20 USD) battery adapters which allow you to use standard SR44 batteries in the Leica CL. I guess in the long run it is cheaper than Wein cells, and the availability is better.
For the US, I think the best shot is CRISS, and in Europe I can personally recommend Frans de Gruijter. Sources are listed in Nemengs FAQ:
http://nemeng.com/leica/012e.shtml