Hi,
Looking around there are a number of crystal radio kits available.
https://www.brightminds.co.uk/products/crystal-radio-kit
You don't need a germanium diode, almost any diode will do, but Germanium diodes (1n34a) are still widely available and due to their lower reverse voltage more sensitive than many other types.
There are many small variable caps in the 300-500pf range, just not the (ex military?) large air spaced transmitting caps that were cheap 30+ years ago.
https://www.ebay.co.uk/itm/Miniature-AM-Tuning-Variable-Capacitor-/290981523...
The ear pieces are probably the hardest item to source , but again ebay has a number of sources. https://www.ebay.co.uk/itm/High-Sensitivity-Headphone-Earpiece-for-Crystal-S...
Derek...
On 28-Sep-18 11:18, Andy Bennett wrote:
Hi,
200-in-one < https://amzn.to/2R0wIkF >
I had this one well over 20 years ago. It was absolutely ace.
It covered a lot of different things. Lots of stuff I understood and lots of things I barely understood until I got to university.
I think it was my 2nd or 3rd kit tho'. I had a super simple one to start with.
Regards, @ndy