Welcome to the forum
have you tried contacting your local vets, sometimes they have people who have lost guineas & want to break the cycle of a lone piggy, or have bought guineas & they have been mis-sexed, so ending up with offspring they didn't expect!
also the veterinary practice may have some smaller rescues on their books that they can recommend? (you could suggest taking to them for a health check/sexing at the vets to show you're committed to owning guineas too).
I got one of my previous guineas from the receptionist at my local vets, she had 3 that had gradually disappeared over rainbow bridge & the fourth was left alone as the kids were grown up &left home she wanted her to have company, she was 5yrs old when i got her but i had her for 3yrs as company for my bereaved girl.
I know you won't want only one as in my circumstances, but maybe the vets will know of some for re-homing.. even things such as allergies developing in one of the children, can be a need for re-homing, when guineas are still young.
I've only ever bought one guinea from a shop (Pets at home) in 20+yrs of owning guineas & she's only about a year old now, but she's very friendly &loves cuddles (wheeks like a diva when you pick her up mind!) i think friendliness & confidence is all down to the individual guinea, their personality generally, also the amount of handling, patience & interaction they receive from you can make a difference to their sociability levels.
good luck in your search, let us know how you get on. you'll still be welcome whether your new guineas are rescue or shop bought, etc.
As a rescue friendly forum we try & promote rescues, where you also get so much more after sales support, health advice & general guidance. But my local recommended rescue is approx an hours drive away & I'm not keen on driving around in a city i'm unfamiliar with either.
keep us updated & looking forwards to seeing pics of your new babies when you get them. xx