Lesu also makes 1/16 axles with locking differential. They are fysically smaller then the 1/14 scale Tamiya ones. In Europe they are sold under the Thicon brand:
https://www.thicon-models.com/thicon...b-sperrbar-3_1
You may want to look for the original branded Lesu ones, but the sizes are mentioned on the Thicon site, so you can check if they are right for you.
The quality is good for the price, and the locking differential works really nice off road.