As quoted from c64-wiki.com :

The Neos Mouse was a third party mouse, produced by the company Nihon Electronics Co. Ltd. (internally Mitshumi), introduced in 1985 for the C64 and C128 at the same time as the Commodore 1350, really a joystick shaped in a mouse form.

Check out this Scuzzblog Diaries post about using GEOS with a NEOS Mouse.