At six weeks, he should be cuddling up to mom and siblings for warmth and security, and I'm amazed your brave enough to bring him into bed with you, I'd be freaking out with how tiny he is! (afraid to squish him) Anyway, how about his?
Brown Mutt Snuggle Puppie SnugglePuppie Brown Mutt Snuggle Puppy
It has a heat packet to keep him warm, and is soft and furry like his siblings would be. Plus, it has a heartbeat so he won't feel alone in the ex-pen. There's different kinds so google doggles snuggle puppy, or just snuggle puppy and it will turn up with different kinds.