Mouse in a mouse

Gross me out with this computer mouse that comes with actual body parts of what was once a sewer rat. This little DIY project requires you to pick up a tiny travel-size mouse (the computer peripheral and not the pest), followed by a similarly-sized mouse from your local pet store. Since it is easier to fit a small object into a large mouse instead of otherwise, it would be better if the former was smaller than the latter. Any extra space left over can always be filled with cotton balls. All I know is I can’t really get any work done with this mouse since my stomach would churn whenever I look at it, let alone touch it.