favorite BBB and BB-xM accessories

I’m writing a book on doing penetration testing with the BBB and BB-xM and want to include links to vendors who provide accessories for the Beagles. Enclosures and other items related to pentesting are particularly interesting.

What are your favorite accessories and where do you get them?

GeoOne Tracker
Alfa wifi dongles

those are the first couple off the top of my head that are easily
purchased. I know I have more things I use, but not at home currently.
If I remember when back home I will post more.