They do make a Jurni for the Fire but it won't fit either. The Fire cases use the speaker holes as mounts. i've written to Marware about Nexus cases and they didn't respond.
It's still a little bit early to get nice cases. some stores were faster or got early access at the convention. Others have said they'd have to wait until after the release to start making them. One would think Marware would make Nexus cases since it's sold in mass numbers already but it never hurts for more people to ask.