You cannot, unfortunately, get a Gallade with Taunt by any means other than TM. Taunt is not one of Gallade's egg moves in Gen IV. The TM is located on Route 111 in Diamond/Pearl/Platinum and in Ilex Forest, Burned Tower and the Celadon City Dept. Store in HeartGold/SoulSilver.
EDIT: I suppose you could trade with someone you know in real life for a Taunt Gallade. Then you're not technically using any TMs.