Dextrose is basically glucose, and maltodextrin is derived from starches. To my knowledge the only foods that would have maltodextrin would be pre-processed in that it would need to be added, and they are most likely countless.
"Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure"
I just got a bag of straight dextrose from the health food store to add to my shakes, $5 for a 2 lb bag, and Carbo Gain(ingredients 100% maltodextrin from corn starch), which was a little more expensive. But you can get 'em even cheaper by the pound from bakery supply stores/websites, before shipping costs anyway. :- /
Oh, and one thing I read when I was looking them up, cause I guess their popular for diabetics upping their blood sugar quickly was Smarties, those little cheap candies in the roll. I guess they're almost completely dextrose, with just a little food coloring and flavoring.