I think going to a good breeder is the best option if there are no rescues near you and no way to get a rescue pig.
Of course there are good breeders, as in people who love their animals and look after them well. There are breeders who look after their animals as well as anyone on here, and they're not the ones who are neglecting animals and abandoning them, they're not the bad guys.
In Ireland there are hardly any rescues that take small animals, and it's almost impossible to get rescue guinea pigs. It'd be easier in Dublin I guess, but that's very far away from me. Good breeders are very hard to find too.
So one of mine comes from a bad pet shop (the pet shop looked fine so I bought her, because I couldn't find any others, but after seeing other shops in this chain with sick animals etc. I wouldn't go there and don't even buy supplies there).
3 of them came from this good pet shop I know. Still I don't like pet shops that sell animals, but this is a small independant pet shop, and they only have a few animals that they get from people with unwanted litters, etc.
1 was the baby of one of my pigs that was pregnant when I bought her.
Of my four other pigs I've had in the past, one was from a pet shop, one was from an ad on the internet of pigs for sale, one was from an accidental litter that I found out about on a guinea pig forum, and one was from the ISPCA.