I found Distributor caps needed Prestolite P3-9

My guess is they aren't too hard to find, just hard to write the check. Have you tried the usual sources?

Hate to say it Ed, but I am not sure who the all the usual sources are for this one all be it I probably know a few and have started asking around (I will PM you my original list I started with).  I do know there are plenty of PI cars out there using a black cap verses the maroon caps (so some sort of cap can be retrofitted or some sort of whole distributor - as well as rotor) - important thing is that it run well and that is not possible with the current caps. One cap certainly would help the cause as you can run it on one distributor.

Ghost Parts in Chardon, OH may help or lead to someone who can.

I believe you are looking for the Dejon distributor caps. The earlier Springfield Phantom 1s used American Bosch distributors. I believe these were discontinued in late 1928 and replaced with the Dejon distributor units.

 Rudy Rosales in Ohio used to sell these but I believe he has retired.

Other possible sources:

http://www.dennisonjaynemotors.com/parts.htm

They specialize in prewar Rolls Royce parts and are very helpful and knowledgable.

http://www.northwesternautosupply.com/

They are a good source for NOS and hard to find prewar ignition parts. They also know what parts listed for other cars might interchange with what you need.

I would try Steve Litton/Ghost parts as well.

There is another guy who has placed ads here and  that has a lot of early, prewar distributor parts. I haven't seen him here in awhile, but, he helped me on some obscure requests. 

Good luck.

Here is the other source I was talking about:

 Tom VanMeeteren Valley, Nebraska  402-359-5762 or tsvanmeet@gmail.com

A great source of obsolete distributor parts and knows his stuff. 

Thanks, I did find a pair of generics in black that are doing the trick - just hate to not have the original maroon with numbers on them and ...