There was a good discussion on the Velo-Orange blog on the topic of chainguards awhile back:

http://velo-orange.blogspot.com/2007...s-are-art.html

Some Simplex chainguards were made to work with particular Simplex front derailleurs, but tracking down the match might be difficult. I think you can do it with your TA triple as the TA crankset has enough room for a chainguard between the crank arm and the largest ring, but it's not a lot of room!

Neal