Are these available anywhere?

I'd just find a condenser. 1 microfarad.

The basic suppressor for the ignition system is a 1 mfd suppressor. Attach it to the LT or positive (+) terminal of the coil on the ignition switch side. There are two types of suppressor connected in different ways, depending on whether your set has AM or FM reception.

[URL]https://www.summitracing.com/parts/smp-rc1#overview[/URL]
Interesting. What type is used for FM? I have an AM/FM radio. It has been gutted and modernized if that makes any difference?