If you have a Wii, you can actually play melee directly off the iso by loading it off an SD card/External hard-drive.
Yeah if you're really desperate, you'll need an SD Card/USB or external hard drive. You'll have to download Homebrew Channel on your Wii then download a USB Loader or DIOS MIOS booter. You have to go through an ass load of steps to get it to finally work, but if you persevere, you can finally play Smash (and any other Gamecube and Wii game) on a TV off of a USB. Seeing as how you're already playing it on Dolphin, you probably already have a Melee .iso in hand, so you should be good to go.
Otherwise, just buy a copy off of eBay.
I could walk you through the steps if you want, but I warn you that I'm not always on so I can be a liability.