Gosh, that's hard at his age. I'd have thought they wouldn't want him chewing anything for a while- 10 days or so, until the extraction sites heal up? I have 2 dogs who have had to have teeth extracted but I don't remember the post op instructions for sure and mine were older, having permanent teeth removed. Eventually we were allowed to let them chew things that "weren't hard" and that's when I loaded up on West Paw toys. The only other thing I can think of that might be ok would be something like a wet, frozen washcloth, which would soften up quickly with chewing. Hopefully it wouldn't give him a taste for chewing fabric over the long run.
JubJub has the most appealingly sweet little face, btw.