W/o a slot 2 enabled DS or a GBA you will need a linker. A lot of proper GBA flash carts came w/ them. You may be able to find a user somewhere w/ a dead flash cart that still has his/her linker that they would sell you. If not, you could buy this.
Seriously though, most GBA ROMs you are going to download are going to be clean or labeled as patched if your source is even remotely reliable. There is very little to be gained from dumping it yourself so that you end up w/ a "clean" ROM. For that matter, if you sent it to someone to dump, they could easily send you a file they downloaded off the net and sent to you as the dump w/o actually having the ability to dump it themselves... How would you know? Hell, I have a linker and a DS Lite I could use to dump your game, but if I already had your game on my HD, whether I dumped it myself or downloaded it, I'd be real tempted to just send you the file from my HD rather than dumping your cart. IF you sent your cart to me I would actually dump it for you, but most people wouldn't, some people would just keep your cart w/o sending anything.
Also, if you give them the cart in exchange for dumping it, you no longer own the cart or have the rights to play it. So if you don't want to download it because of the piracy issue, well, you would be the pirate whenever you used the ROM image and the dumper would be legit as you just transferred your ownership of that software to them.
Seriously, just download it. Or buy a used GBA or knock off GBA from your online Chinese shop of choice and play it on that.