This looks like a possible solution. http://broadband.motorola.com/consum...oducts/sbg900/
Not sure wheter it works with a Mac or not, should, since I can't think of much that would cause it not to work...
Whatever you do, don't end up with a Scientific Atlanta WebSTAR Cable Mode/Wireless in one. They are terrible.
EDIT: It states, works with Windows 95/98/NT/ME/XP, Mac OS 8 or higher, and Unix.
Be sure to check with your cable provider that it's supported. Time Warner supports it here.
From what I see it should work,