If you're looking for a standard size, and not something custom, I think your best bet would be a LFS.
Once you know what size you want check with the local stores.
Pet's Warehouse is a big store, and often has pretty good prices. I think they sell Oceanic, which I would look into before buying. Their quality has not been spoken well about recently. I don't think there's a lot of markup on tanks, so I'd expect most places to have a pretty close price to everyone else.
Fishy in Bayshore sells Perfecto and AGA, IIRC.