Drawing on top of HTMLViewer content

In my app I have a HTMLViewer displaying Google maps. On top of that I have a Canvas where GPS tracks and various data are drawn. This works fine with Google maps.
I wanted to improve this by adding OpenStreetMaps and Bing maps, but; That’s not as simple as I imagined. It’s not a problem displaying the maps, but they are apparently rendered differently than Google maps, as they renders on top of the canvas - which sort of ruins the experience as no GPS information is visible.

Are there any way to force the canvas graphics to be rendered on top of the maps? Or do anyone have a suggestion for a workaround?