Doesn't exist, not for your application
I *JUST* set myself up for the exact same bike (BFD is the best bike i've ever owned - likely the best bike ever created
)
What i did is replace my fork with a steel 135mm (eg Classic Mtn Rear) fork, and build a rear non-offset-side wheel on a rear motor. I swap the motor on/off, so i pressed on a crown race, and replace the whole front fork.
What i
My build:
Grin GMAC build (proper torque arm, _geared_ regen braking can bring whole bike to a stop by itself, power capable to be durable long term on a loaded bike PhaseRunner controller 52v 14ah 52v pack (the 21700 model was on sale) soma battleaxe 135 fork. Might replace with a surly fork when the non-side-offset versions get back in stock. (the three options i found that could be had new: surly pugs or moonlander NONoffset (not in stock), soma battleaxe (some old stock to be found), and a steel fork off of a tumbleweed bike (can be bought new, in-stock).
Some details:
Cargo is a challenging application, for both torque & weight load, as well as power. This limits your realistic options. Grin strongly advised against an small motor such as g301, for instance, even though I am only wanted a "1x human" (~250w MAX) build) regen braking is a huge plus, to save/augment the brakes (only ~10% range recoupe MAX, likely ~5%)
hope that helps! Look at my thread history for more details, i asked some of the same questions here.
