I’d actually like to see a d8/d4 hybrid. Basically take a caltrop d4, snip a bit off the ends to make a truncated tetrahedron. You’ll then have 4 large hexagonal faces and 4 small triangular ones. Put the numbers on the triangles. If it lands upside down, then it is just house rules whether to use the bottom face or to reroll. Or just number the large faces too.

It’s a similar concept to the round safety d4s; just less… round.