Use the Pink horrors kit, it comes with a few "beakies".

That crab claw you get from a daemonette or a possessed
CSM, the back of the head could be a ripper, body could be a gaunt, legs also a gaunt, but those tiny arms.. either sacrifice a poor grot or make 'em out of
GS. Same with that eyeball arm, which is actually cool as hell.. hold on, I'm going to tear apart my nasty old nids now