freestompboxes.org

...are fake

I've just open one up and what I've got inside is aluminum and foil

Here's item description https://cgi.ebay.com/ws/eBayISAPI.dll?V ... K:MEWNX:IT

And the seller name is https://myworld.ebay.com/orpheus_2005/

I have more at home, but they're lost for ever, as well as $700 in parts from my flooded basement

BTW, you know what makes me laugh? There is a PUP maker who sells exactly the same caps as a bumble bee work alikes

They should have aluminium foil in them along with paper which has been oil impregnated. The paper is likely rolled on one side of the foil.
And Bumblebee caps are paper in oil, so I'd expect sellers to claim that other PIO caps are equivalent parts. They may not hold the same mojo, but they're the same thing after all.

I've got a few of these so I'll cut some up to see what I can find.