Hi
@momido
I do live fairly near Zurich and spent A LOT of time trying to find guinea pigs to adopt.
The closest place is probably the Zurich Tierschutz - it is next to Zurich Zoo.
Zürcher Tierschutz :: Tiervermittlung
However what I would say is that the minimum cage size they will even consider is 2m square, even for 2 piggies.
That works out to be a 7 x 7 C &C cage.
We applied to adopt a 4 year old male who had been there for several months with no interest (he was a biter) but were turned down becasue our cage was 'only' 10 x 2 C&C.
Plus they allowed us to come and see the guinea pig, which meant my daughter fell in love with him, and then when we officially applied we were turned down.
It was quite upsetting as we had already been honest about our cage and sent multiple photos etc. so assumed that since they said we could come and meet the guinea pig that they would be prepared to rehome him to us, but in the end said our cage was too small despite being over 3 meters long!
Another route if you are looking for an older guinea pig would be from a licensed breeder.
There are a few around and most offer a variety of ages and types of guinea pig.
However be prepared to pay full price - even for an older animal.
If you want more specific info let me know - I know of a couple of breeders in the Horgen/Schindellegi area.
Good luck finding some more piggies.