I have a Belkin Cushdesk and a Belkin Cushtop, but they are basically made for laptops. I think it would be very difficult or impossible to use a mouse on one of them. Not wide enough for a keyboard and mouse.
Although if you got a keyboard with built in trackball or trackpad, they would work.
Think I got mine at Costco. You can see pictures of them on the Belkin website.
But I don't think I've ever seen a lap desk wide enough for a full keyboard and room to use a mouse.