Does any other mfg make a truly floating worm or craw other than Z Man products?

Yes.  A number of them.

The buoyancy of some will be negated by putting a hook in them, however. 

Any soft plastics made without salt naturally float.

 

Allen 

Gambler makes a good one. 

https://doublezlures.com

Damiki Air Craws

 

With a Lindy worm blower, you can make nearly any soft plastic float.

I use Zoom trick worms and they are available in any color you want.  Zoom likes to say they are the original floating worm.