First One, that we love while staying down in Southern California near Los Angeles is Yamashiro Farmers' Market. Not only do they offer great fresh produce, you can hangout and sip wine while enjoying some great acoustic jazz. We stay at a couple different RV resorts and just drive the toad to the market.
www.lacityfarm.org/yamashiro.cfm
Number Two, is up north in California in the San Francisco bay area called Ferry Plaza Farmers' Market. Like Yamashiros they have abundent selection of produce, along with a great selection of local cheeses, meats and varietly of local area crafted foods. Same sort of thing, stay out and about at a northern area RV resort of your choice, drive in do a nice days shopping while maybe checking out your favorite sights. There website is
www.ferrybuildingmarketplace.com
Now these are not the only ones and I realize they are not all that easy to get to and I don't recommend trying to park your large Newell, these are just favorites of ours while visiting the larger metro areas in the winter month away from ND.
We will share some others as we think of them in other parts of the country where we have visited.