Here's one I have used:
Silk Screening Supplies .com, screen printing equipment, silk screen printing kits
Or there is
http://victoryFactory.com
Check your yellow pages for printing supplies, if so you can go and look and see what they carry along with not having to pay shipping for your items which will save you some money as well.
Here is one I found somewhat near you. Not sure how far away this is from San Diego but they are local.
Westix Escondido, CA - YELLOWPAGES.COM