This guy is a local cap vendor (I buy from him at swap-meets) and stocks dial cord and dial lamps as well as yellow film caps and lytics.
http://www.radioantiques.com/
Some hardware stores stock rubber grommets if you look through the drawers (IIRC Ace hardware is one).
Madlabs: I fixed the series parallel resistance value thing, I noticed I got it backwards (sometimes I have to finish typing fast and skip a proof read) before I read your post...However I agree with old coot the effective wattage of the pair doubles in both configs. In college I proved that mathematically a few times and can do it again if you doubt us.