Don't do it. Just get a new one. There are even some medical ones you can buy that are solid covered. Do you know though that tests have shown that keyboards are harboring bacteria? I wash my hands after using a community board at work. I also read the other day that shopping cart handles are germ hotels too. Sigh. My favorite two places to eat. (in front of the computer and shopping during lunch)
Don't lay your food in the shopping cart tray where toddlers and babies ride. You know what they do.....