Just so you know, San Francisco has NO Walmart and NO TSC!Walmart and tractor supply are both open and carry chick feed (and ship to home). Any other poultry feed that is NOT layer would also be fine... starter, grower, flock raiser, all flock, meat bird, etc.
Some standard grocery stores may also sell small bags of chick feed in their pet departments.
The info in post # 2 is good for short term purposes...
If you can't find feed at a store, consider posting an ad on Craigslist farm and garden section for someone who might part with a little feed from their supply... Petaluma is like the chicken capital at one time... lots of chicken farmers in that area.
ETA: don't forget it isn't just protein but amino acids that's key. Chickens are omnivores... those babes will eat meat also.. cooked ground beef (maybe raw), chicken, tuna, etc. Grit can be a pile of dirt. Corn meal should be a bit higher in protein than standard corn.