I'm using this app called Router Keygen.
It has a library with basic router key's.
Works for most Thompson and Speedtouch router.
Just google for Router Keygen APK and i'm sure you will find the right one (downloaded it on FileCrop)
As I am a new user i'm not allowed to post links
But google for "Router Keygen APK" and than the 1st link, that one will do his job