chances are, youre not going to find a wireless keyboard with a numpad that is also a slim model. slim wireless keyboards are for multimedia - that is their sole purpose, or their "raison de etre" if you want to be condescending. numpads are for data entry - that is their sole purpose. no data entry profession has a need for a wireless keyboard, and no HTPC setup has a need for a numpad (besides us). i have a feeling you are, for lack of a better word, fux0red.
thats just my surmization.
oh yeah, if you need a keypad here is a cheap USB one for $10 that comes with a USB snakelight thing (obviously intended for laptops). great deal!
http://sotechs.com/ComputerDeals/Pro.../Discount/1337