Got an email about this mouse. Has 5 star reviews on Amazon. This seems to be a good option for Smart TV boxes or your tablet/PC in general. Currently at £7.26.
Description:

Pictek 2.4G Wireless Mouse is a new high-grade Wireless Mouse with 2400 DPI 5 adjustable levels 6 Buttons. Reliable mouse with plug-and-play, nano receiver, long battery life, ease-of-use, and user comfort, this wireless mouse gives you fast data transmission and no delay or dropouts.

NOTE:
1. Apple computers( Mac OS) does not support the mouse's customized(programmable ) function as some functions of Mac OS is not open to public. But the mouse's normal function still can be used in the Apple computers or Mac OS.
2. If you want to customize buttons,you need to download software from relevant website(written in the user manual). For this mouse, please choose "For 5Keys" installer.

Warranty:New Brand, 45 Day Refund, 18 months Warranty Guarantee!

Specification:

Color: black
Mouse size: 103.5X 70.5 X 38.6mm
Number of the Key: 6 Buttons
DPI: 800-1200-1600-2000-2400
Power Source: 1*PCS AA Battery(Not included)

Package included:

1 x mouse
1 x USB receiver