What kind of supplies are you looking for? Kits & parts? Wouldn't it be problematic to get engines/motors, igniters, and certain chemicals onto flights?
If kits, the selection is slim and the prices are high. Mail order is definitely the way to go.
Fry's (San Jose, Sunnyvale, Campbell, etc), as people have mentioned, does have a tiny selection of kits & motors, and the best part is that they price match (online included).
Hobby Lobby is quite a bit further south in Morgan Hill. Use the 40% coupon as
blackjack2564 suggested. Kits, motors, wood, glues, paint, etc. though I haven't visited in a long time.
I haven't been to these in a while so things may have changed. The kits are pricey and the selections are/were small so I don't think any of these are worth the trip except for possibly the first, so...
- HobbyTown in Sunnyvale has rocketry stuff. Expensive, full hobby store w/a small-mid sized kit selection, motors, building supplies, etc.
- Talbot's Toys in San Mateo is way north (mid-peninsula). Expensive, full hobby/toy store w/a tiny kit selection. If interested, ask for an Estes catalog (free) if available.
- Hobby Co of San Francisco is 40+ miles north. Expensive, full hobby/toy store w/tiny kit selection. Likewise on the Estes catalogs.
Some
Michael's and ToysRUs used to carry kits and motors, but I haven't seen them sold in years. You can definitely pick up building supplies at Michael's though (balsa wood, plywood, dowels, glues, cements, paints, etc). Again, use a 40% coupon per
blackjack2564.
If anyone has more to add, I'd be interested. Good luck and happy hunting!
ps - If packing liquids in your check-in, don't forget to bag them in plastic in case the pressure differential causes them to ooze.