Both the mods I linked are vw, and both at $100 or less. The Zmax version 2 is the better of the two.
The acrylimax is the working of a Zmax version 1.
The Powertube Zmax is version 2, which has added improvements. I don't know if the discount code still works - it was a great deal with 20% off.
I won't link them again - all the info is in my first post.