I kind of hate to say this but toggle bolts really suck for very thin walls. They require a really big hole in the wall in comparison to the screw in them. They will hold well but there are a couple of better choices.
I would bet that the screws used to hold the handle are no bigger than #10 and the total skin thickness is no more than 3/16". A product made specifically for thin brittle materials are Jack Nuts. The whole required to install them is as large or larger than a comparable toggle but when finished the whole will be just slightly larger than the screw used to hold the handle.
A very similar item would be a Molly Bolt.
Both can be installed easily in foam filled walls, while Toggle Bolts are somewhat difficult.