I rather like the idea of the homebrewed one! It could be quite a good learning aid too.....
If nothing else it would provide some nice vintage knobs and switches and probably a useful airspaced variable capacitor which if sold separately would likely recoup its purchase price at £20!
A trawl of '50s '60s radio mags might even turn up its details in an article there
This:
https://www.ebay.co.uk/itm/154495167261
might be worth a punt. Only just out of production!