electrical supplies retailer in downtown LA

Anybody here have a favourite electrical supply store in downtown LA (or within easyish driving distance of downtown) which would stock 30A rack-mount power strips fed through a L5-30P twist-lock plug, with output through regular 15A three-pin receptacles?

Please reply off-list. I can summarise privately if anybody else wants to know the answer.

(Apologies for the non-general-purpose question on this list. I've spent at least a day trying to find this out in other ways before resorting to making this noise, for what that's worth.)