Does anyone know of a kit that converts the e-maxx to a single speed.

slow poke

Take one screw driver.
Disconnect the shift rod from the shifting servo.
Remove the shifting servo mount screws.
Disconnect the shifting servo from the Reciver.
Remove the Shifting servo.

Did I miss anything?

Gorilla makes one, weight savings 50 grams in just the trans include the servo, linkage wires, etc. Much better than just removing the servo, you still have to keep the shifting rod in place, I suppose duct tape might work.

Something to keep it in gear would be nice.
I made my own by taking out first gear and putting in a spacer to hold the shift drum in second gear. So far so good. I also did all the above as well as taking out all the internal shifting hardware and plugging up the holes.