I ahve been after one of them since I bought my NC20 Netbook. This mouse does not need a dongle because it uses the internal bluetooth which comes with most netbooks.
The cheapest I found this online is £17 but today atthe toshiba outlet (Cheshire Oaks) they were selling them for £11.74.
This is ON STORE ONLY DEAL. Link added for reference only.
Wireless Optical Bluetooth Mouse - Silver
Part Number: PA3573E-1ETA
With an operating range of up to 10 meters and easy navigation with 2 ways scrolling, this Bluetooth Technology Mouse offers precise and smooth operation on most surfaces.
Main Features: Interface: Bluetooth 2.0; Frequency: 2.4 GHz; 800 dpi; Profile: HID; Button count: 3 with scrolling wheel; Mouse sensor: optical; Operation range: 10 meters; On/Off switch; Includes 2 x AA Alkaline 1.5v batteries.
Dimensions: 58(W) x 98(D) x 38(H) mm Weight: approx. 61g