Since I found no similar model freely available to the public, I created this model of the Beastboss on Squigosaur. Everything is done from scratch.

I'd recommend printing this only on a resin printer. With the 80mm base, it barly fit a borrowed Mars 2 Pro, without Base it's easier.

Also check out the Squighog Boyz I did:
https://www.thingiverse.com/thing:5925689