[TenTec] Source for 470 pf doorknob capacitors

[Peter Klein]

Can anyone recommend a good source for the 470 pf doorknob capacitors that can replace the switched-in ceramic disc caps in the Ten Tec 229B antenna tuner? After thinking about it for a while, I've decided that I would like to make that mod on some rainy day this fall or winter. 

After all, while a flux capacitor is desirable in a time machine DeLorean, a fluctuating capacitor in an antenna tuner is annoying. :-)

Thanks and 73,
Peter, KD7MW

--Peter, dictating to my iPad
(If it misconstrues, please excuse)