I usually make my own... but I have bought a really good ginger-sesame marinade before. When I get home from work, I'll get what brand it is.
I almost exclusively use extra firm tofu, and I just make sure to leave enough time for the liquid to drain off.
I've seen tofu already marinated at my local health food store. They have a variety of flavors, but it's a few dollars more than just plain tofu where I live. If you can afford it, it might be nice to try.
One more thing... If I feel like I'm getting in a food rut, I'll take a vegetable I either haven't tried or thought I disliked and find a new or different way to prepare it. I've discovered that I like both radishes and turnips by doing this!