There are tons out there. And that depends on what you'd call a
40k model. Basicly any SciFi model might be used for
40k. There is even a topic here on dakkadakka exactly for that purpose, you've probably missed it due to it beeing sticky and all.
http://www.dakkadakka.com/dakkaforum/posts/list/373197.page
Just look in there and start digging through all of those companies for whatever you need.