I am sorry you have found some people's responses rude, it's not intentional, everyone on this site has a lot of experience with pigs and just have the best in mind. I have gone from having upset guinea pigs in a little pet store cage to a big c&c so trust me, it makes a difference.
If you can look around at getting supplies you can build your own c&c cage for very very little, and they're so easy to do. If you go to the home page of this site, it shows the recommended cage sizes for different amounts of guinea pigs. Pet store cages, with their tiny sizes, aren't good for a guinea pigs health as they do not have the space to run, play, or even get away from their poo.
I understand that you have a lot of animals but it is a fact that guinea pigs need a friend. Instinctively, they are herd animals, and are very social. Even though you may pet it lots, they need one of their own species to talk to and play with when you aren't there. It makes a huge difference to their health and their happiness. Lonely guinea pigs get depressed and may be more likely to get ill quicker. It's also said that a happy pig has a longer life span.
Please consider getting a good sizes cage and a second pig - second guinea pigs cost VERY little, just the bit of extra veggies. But it will be so worth it.
If your Mum says no please ask her to look at this site, do a bit of research, and explain to her how important it is. Both you and your pig will be so much happier if it isn't lonely.
I must point out that if you can't pay for this, please bare in mind the costs of:
bedding
veggies (they should have some daily because they can't produce their own vit c)
medicine if necessary
dry food/pellets
hay (which they should have access to 24/7)
I understand that you're young but there are plenty of things you could try and do for money - dog walking, car washing, general chores, even mowing lawns. Perhaps you could get a job doing something simple for a couple of hours a week.
I am going to say something you probably won't like - if you put your guinea pig in a cage that's way too small and don't want to get it a friend or even try it with another pig for your convenience rather than the pigs, then it is cruel and ignore the needs of the animal. It'd be like having a sick dog and leaving it to suffer. If you cannot provide these things for your guinea pig I would suggest getting another pet, like a syrian hamster, which are solitary and don't need massive cages.
Everyone on this thread who you think has been rude has been trying to help you. We all have the guinea pigs best interests in mind. Please remember that, especially when @
lissie is a moderator and could have 'locked your thread' as you requested, but she didn't, because she wants to help the guinea pig you are going to get and help you in understanding those suprisingly complex little animals. Yes, nobody answered your original question, but that's because none of those cages are big enough. I would advise taking another look at the one lissie posted and having a look at buying your own materials to make one (I promise, it's dead easy). All you need are cubes, coroplast and some cable ties. I'm sure everyone could provide you with places to buy them.
EDIT: Now that I've said that I'm not actually sure if it's moderators or admins that lock threads. But even if lissie couldn't have, she is a valued member of this site with some fantastic advice to offer and a lot of experience with guinea pigs, so like I said, it would be worth taking a second look at the cage she linked you too because she did it for you and your guinea pigs benefit, not her own.