I'm in OC and most of the petcos and petsmarts around here have frozen rodents - I'm not sure if they do where you are at in So. Cal but you can check - they come in small packs of like 5-10 depending on size.
Otherwise I've found for us west coasters The mouse factory (http://www.themousefactory.com/) is cheapest on shipping - you can order by the 25 pack and although they are vacuum sealed - once you've opened them you need to use them in a couple of months or you'll get freezer burn on them.
For just one snake you might want to consider pre-killed food - just go to your nearest pet store pick up a couple of mice/rats kill and feed. You can pick up half a dozen, kill them yourself and put them in a freezer bag for the next couple of feedings.
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Tosha 
"Nihil facimus sed id bene facimus"

6.34.0 Ball Python (Harry and Fluffy and gang)
1.0.0 Angolan Python (Anakin Skywalker)
0.0.1 Green Tree Python (Verdi)
0.1.0 Bredls Python (Smurfette)
0.2.0 Feline (Pippen and Pandora)
0.0.1 Desert Tortoise (Pope John Paul aka JP )
2.2.1 Fish (1,2,3,4)
0.0.0 frogs rescued from pool skimmer
0.0.1 Lizards of unknown origin