I'd realy like to help but the actual art of making unique items is still something I'm working on, but I can tell you trying to use Malak's isn't possible right now since his body and head is one model. Bandon's body and head are two different models so it is possible. I do know that Jackal put out a mod awhile back useing the mdl and mdx files for Bandon to make them scout clothes I do belive someone did put out a mod of Bandon's armor as robes like you're trying to do, do not let this stop you though, each person's work is great. The best I could tell you is check the Do you Want to mod SW-KotOR? Then Start here. (
http://www.lucasforums.com/showthread.php?s=&threadid=124284) thread. You will probably need a hex editor to mod the mdl file in order to have a different texture then the one Bandon alredy has. I hope this helped a little bit if not just ignore me and wait for a real modder to try to help you.
EDIT: Here's a link to what someone, named HULAS?, has done mabye you can get some clues to help you from what he has done. Darth Bandon Robes (
http://www.pcgamemods.com/6852)