I have been pondering the same problem for a year now, and have decided to
do nothing.
Table saw dust is heavy enough that it just falls to the floor without
creating too much mess, so I don't think it is worth the effort. You will
have to get the saw almost airtight to be effective, and even then 75% will
be thrown forward by the blade. The only real solution is a over the blade
hood, and I can't justify that.