I use a non branded Amiga to USB mouse adapter i bought from ebay. The guy was selling loads at the time for iirc around 10 or 15 euros.
PROS: No need for drivers and works 100% fully with anything you throw at it, Early-startup, Workbench, OS3.9, All games. The lot. Just as though you are using an Amiga Mouse.
CONS: Forget the scroll wheel or the 3rd button.
