I like Buzz, have their drawer system. On the website it doesn't provide any info on the rear brakes, just a few photos.Concerning the lack of an aftermarket rear brake system - Buzz Overland makes a full ( front and rear ) big brake kit for the Grenadier. The e-brake is even hydraulic. You’ll find a few images of this within my build thread:
https://www.theineosforum.com/threads/snuffleupagus.12420527/post-1333369549