I recently replaced mine for the very same reason. I got mine on Ebay for $20.00 including the mast. When I checked, I think the base was around $35.00 without the mast, they were sold seperately. I'm not sure if the Matrix one is the same, but if it is often stuff is cheaper from a Toyota dealer.
I tried the shark fin route. Not a good idea. The OEM antenna base is actually quite a well made complicated part. It has a signal amplifier built into it. I got my price from an online GM parts dealer, can't remember which one. I can't find the Ebay seller's name, I've got about 400 feedback.
Interesting how it seems in the last couple of months antenna base damage has been rather common.Here's a thread to my experience a few years back:http://forums.genvibe.com/zerothread?id=5967
Would you agree to debris acceptance? 2003 Vibe GTMods installed GM Top and Mid-Gate Spoilers, Cosmo CAI, TWM Short Shifter with Desert Eagle weighted shift knob, TWM Bronzoil Shifter Cable Bushings, Magnaflow Cat Back Exhaust, Unichip, Injen Billet Aluminum Engine/Sparkplug covers and oil cap, Optima RedTop Battery, Lineage Ground Wire KitAwaiting install: Energy Suspension Motor Mounts, DC Sports Header