I've owned a couple of pairs of those. They work well, and I doubt they are still around.
An easy DIY option is to buy a pair of these:
[url][/https://www.parts-express.com/dayton-audio-amt-mini-8-air-motion-transformer-tweeter-8-ohm--275-095url]
Cross them over with a simple 1 mf capacitor in series, adjust the output by using foam or felt over the openings, which is how VMPS did it. Wire them out of phase with the main speaker.
It works as well as the VMPS for less $.