Hi Dave, I'm not entirely sure about this, but Ludwig has currently been doing re-issue kits, so there might be the possibility that a current, new Telescoping L-Arm ordered from ludwig through a dealer might work in your application.
Like I say, I'm not sure about the Rod Diameters between new, and vintage. and whether a new Rod will insert into your bass Drum Cymbal Arm mount?
I'm sure calling a good, knowledgeable ludwig Dealer, perhaps someone like the Drum Pad in Palatine, Illinois would know. Lots of good, knowledgeable, helpful people there. (Perhaps someone here knows the answer to this?)
I don't have personal knowledge of exactly where in the country you live, but there are Vintage Drum Shows all over the US, and coming this spring, there will be the large Vintage Chicago Drum Show, usually held in St Charles, Ill. Others would be the PA Show, and there's also a Hollywood Show, plus many others across the country.
Literally hordes of people travel clear across the country to attend these shows, and they are tons of fun. Drum Celebrities usually attend, as also many vintage collectors, and dealers.
You should be able to acquire the proper time correct parts for your set at these shows. There are always lots of snare drums, and cymbals too at these shows.
mark