Alternator Changed...Battery Still dies

A DVM would great to diagnose the issue. you can probably pick one up fairly cheap at auto zone. Without one, its going to take a lot of extra time to diagnose it. Disconnect something and let it sit to see if it kills the battery, if not, move on. I would start with the alternator for sure cause its the most likely suspect. After that, Ignition coil, brake light switch, and maybe the ignition switch itself.