So - not sure on the portable part. I don't know of one that would check that box

But - our friends here just got the GE Opal, countertop. And it make that good / soft / small cubes. Like the old school stuff. And, it makes ice very fast. Like, he and I were drinking mix drinks the other night (at a manly pace I might add) - by the time we made another drink the ice was replaced.

https://www.amazon.com/GE-Profile-Countertop-Nugget-Maker/dp/B07YF9SGBW