You can get the security bits to open your TomTom rider at amazon.com for less than $10 with shipping, or they are even cheaper at a Harbor Freight store.
Below is a link to a video showing how to open a TomTom rider.
http://www.youtube.com/watch?v=j9_MF7EuLuQ
Stuart Ferguson
March 2009
If its the same as on a TT One then u need Torx 9
But with open tip. (hollow point)
Where to buy?
Any good hardware (tool) shop should have these.
Perhaps good idea to buy a set of torx "bits" because inside you'l find T6 sized ones.
Arnold
February 2009
Automatic Answer
While you wait for answers, we may have found some information which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix satellite navigation.