Buying a car prepped for trackdays in Germany?

[mft]

I live in Switzerland, and am interested in picking up a car already modified for trackways (i.e. seat, cage, etc.) - does anyone know of any websites which might help, or alternatively likely search terms for the main car websites? (searching for 'ringwagen' doesn't help, for example.)

(I've also asked this in the Swiss forum, but I suspect Germany is more likely.)

Thanks