Look into laptop lap platforms. You can get in them in all manner of sizes, shapes, some with padding on the bottom, some with lips to keep laptops (and in your case, keyboards) from sliding down against you, some vented to keep you from sweating from having it on your lap all the time, etc. There's no good solid answer but try searching "laptop lap desk" on online shops or Google and then see which would have the size you need for your keyboard and mouse pad. I have even seen a couple that you can attach legs to in order to turn them into mini stands!