In the manual I found it looks like there is no slipper it’s a full lockout, so you just need a 32 pitch spur and then drill it to fit that hub. Something 56-48T and then just pinion it to effect
Help me decide on this product: Traxxas 6842 0.8 Metric Pitch Spur Gear, 50T
https://a.co/d/gdmkv35
See if that link works. How I would attack the problem is buy something like this Traxxas 50T spur. Mod 0.8 and 32pitch are interchangeable. Amain specifies your stock spur as 32p. See if the center bore of this Traxxas spur will fit over that 4 bolt spur hub you have. If it’s too small drill it out. Then line up one of the 3 spur bolt holes with one of the 4 bolt holes on the hub and bolt it. Spin the assembly and see if the hub is centered on the spur. If it is, drill and bolt the other 3. Put it in and test it. If it works, buy the metal aftermarket replacement for that spur and repeat.
It would have been easier if there was a 4 bolt spur gear to try but most of them are 3 or 6. You actually luck out that it’s a locked spur setup and not a slipper because then you don’t have clutch pads and plates and all that to deal with. It seems like the manufacturer was thinking about it at some point because of the hexagon recess in that spur like a team associated or axial hex clutch pad
This team associated spur has an 8 bolt outer pattern you may want to try. If it lines up with your 4 bolts super lucky. If not, I wouldn’t be comfortable drilling into that, not a lot of material to work with
Help me decide on this product: Team Associated 7663 66T 32P GT Spur Gear
https://a.co/d/5uUKnxa