There are a few options. A lot of stores carry Amy's frozen pizza - she makes one that is gluten free and lactose free (made with soy cheese), but personally I'm not a huge fan of her pizza. For frozen pizza, I like Glutino's better (they have at least one variety that's made with soy cheese). They're a bit harder to find, but if you have a Whole Foods near you, most carry Glutino's. You're other option is to make pizza from scratch. There are some pre-made shells out there (Glutino, Kinnikinnick, or Whole Foods Gluten Free Bakehouse) which you can top with the sauce/cheese or your choice (I'm not sure if any of these are lactose free). Of those, I prefer Glutino or Whole Foods -- the Kinnikinnick crust is a little too sweet for me. Ian's also makes a crust mix that is my new favorite (it's in a yellow cannister with a red top)...I'm pretty sure this is lactose free. You just add water and a little oil...it comes with sauce and you add your own cheese. It takes a little planning because you need to let the dough rise for 45 minutes, but worth the wait in my opinion.
Hope this helps.