I got them from Home Depot in the tool section with the safety tapes and things like that.
Of course those had to be the most expensive dang ones there are, but I liked the diamond pattern enough to pay 10 bucks plus tax for 4 stickers than I only needed 1/3 of two of them.:D
I don't think they would work in a curved housing surface though, as they are fairly stiff.
Sticky as hell on the backing, but still.