I had never heard of one either, so I looked it up and found nothing by the name. The closest thing I could find to the description is these, and I’ve got to say, I like how they look. I’m curious if this is actually the type they were talking about though.

I guess they’re usually called “rounded d4s” but I think they look like two of those classic spacetime wormhole depictions put together.

Edit:
These dice (top left):

Looks to me like two of these wormholes, one rotated 90 deg, and smooshed together: