I would pin it.
Use wood for pins if you have to, the tougher the better of course.
They don't need to be perfectly round or smooth as the GG will fill any voids from whittling marks.
Something like Oak would be better than Pine if available.
You can drill/dig out the pin holes in the scales with a sharpened flat blade screw driver if you have one small enough.
Also the awl on a SAK would work in a pinch.(assuming you have a SAK with an awl... as everyone should.

)
Be sure to clean & rough up the tang of the machete and the wood slabs for good glue adhesion.
And throughly cover the pins with glue (no matter the material they're made of) before inserting them.
Annnnnndd..Good luck.