It's probably too early for many 3rd party alternatives to have popped up. As for full models, a search for space dwarf miniatures will carry you far.

And I can recommend Ramshackle game's drill pod as a centerpiece or terrain for any Votann army: https://shop.ramshacklegames.co.uk/home/211-BoringMachine.html

Maybe, I'd check etsy! Or even ebay? Not sure exactly what kind of bits your looking for though.  I've seen a fair amount of people swapping out the heads for karadron overlord heads (AoS).

There's a lot of stls already for helmets and kin head replacements.

I think Taro modelmaker is working on an Ironkin head?

Though if anyone knows good STL's that'd be great

Been looking around and only found one item that could be used with votann on a bunch of sits but wondering if anyone has found anything for the leagues that works

Any 3rd party bits that work with or are made for squats ?