It would take some very careful carving, but try to make like a vortex bowl out of an apple or pear. I'm going to try this later with an apple and some Nakhla Double Apple, i'll post back with pics and tell you guys how it went and if it worked out well i'll type out how i did it
Ok i wound up making the vortex-like bowl out of an apple, and it was pretty easy and i got a good smoke out of it. I took pictures that i posted below. Here's how i went about doing it:
Cut about 1/4 of the apple off the top
Scooped out a ring with a small melon scooper on the outer part of the apple on the top
Used a knife to make the smooth curved edge where the scooped out ring met the middle of the "vortex" to make a clean vertical surface to punch holes
Used the downstem of my hookah to make a hole from the bottom of the apple up through the middle of the bowl, so that when i punched holes in the vortex it would smoke
Poked holes in the vortex in the middle so they'd meet the hole i made at the bottom with the downstem, then blew in it to make any seeds/leftover apple not clog the holes.
Just used a knife to make the bottom of the apple fit to the grommet on the stem