I just heard about the Bekin building, which is being converted into studios of varying size. They don't seem to have any available at the moment, but you might inquire as to their pricing, etc. They are located in northpark, here's their website:
http://www.thebekin.com/ I know there are a few places downtown too, but this one seems more permanent (1 year leases). You might also ask at Liberty Station, they have studio spaces available there, some big, some small, but I am not sure of the pricing. At least at Liberty Station you might be able to sell out of your studio, but you will also have pedestrians wandering by and sometimes watching you. :P