I do have a Pokémon Sapphire, but it's fake. It keeps deleting the save file each time I attempt to trade between other Pokémon GBA games or even transfer Pokémon to Diamond. Even replacing the internal battery didn't work.
Oh, by the way I live in the UK so I won't take "Gamestop" for an answer. I also refuse to buy online cause apparently everyone gets fake Ruby/Sapphire/Emerald carts over the internet.
As I'm not from the UK, I'm not too familiar with the stores there, but if you refuse to buy from Gamestop and from online retailiers, there's not much I can do to help. But I can refer you to this youtube vid that shows how to tell fake gba games from real ones.
I recommend a store that deals with old/used games. Not being from the UK either I can't give any specifics but in my neck of the woods, we have a store called Get Your Game On that specializes in old games, old systems etc. and I was able to find a genuine copy of Ruby and FireRed/LeafGreen so maybe there's a store like that you can go to.
I also refuse to buy online cause apparently everyone gets fake Ruby/Sapphire/Emerald carts over the internet.
People who get fake carts are people who jump on deals that are too good to be true from sellers that are not reputable. Your two options are to either find a used game shop that has them or get them online. Both eBay and the Amazon Marketplace have sellers with solid return policies and thousands of positive reviews (most of these people ARE used game shop owners that take advantage of a larger online marketplace) that you can get a used game from, or if you're really apprehensive you can shell out the extra money to get a new copy of the game.
Also, don't think for a second that you won't have the same chance of getting a ****ed up cart from an actual store. You don't know what kind of irresponsible hacking and mistreating the person who owned it before you has done, and there's a good chance you won't see the effects of it until after the warranty runs out.
Unfortunately, buying these games now is going to be a gamble no matter how you look at it.
QT x314159. glory of power metal is an anagram of Lame Flowerpot Orgy. ~ kirbymuncher