It's a simple ball valve that blocks the fluid from flowing back when the brakes are released. The one that Van's sells is a double ball valve with a lever that can be controlled by cable at a distance..... Still just a ball valve, and no more a parking brake than a simple ball valve.
If you want a cheap parking brake, just make a Y bar that will press on the brakes and wedge against the spar. And to make it better, add a spring in the shaft to apply a continuous load on the pedals.
That exact same valve (I know 'cause I have a dozen of them) is available in the Aviation Section of the McMaster-Carr catalog for $9.46. It's just a plated, brass 1/4 turn mini valve - ain't nuthin' special ...
I’ve never felt the need for a parking brake on a GA airplane.. I can either taxi the tailwheel into the grass or gravel, or park perpendicular to any slope.. then jump out and chock it. To leave without the plane rolling away, I place a pebble or stick behind the tire, remove my chock and jump in. My reluctance to have a parking brake is because one day, my buddy was test flying a new build, the owners installed a valve, but didn’t hook up the cable to the handle. The handle shook into the closed position and after landing, he applied brakes and the brakes applied but wouldn’t release. Had he “tested” the brakes on short final (or applied then after liftoff to stop wheel shake), it’s possible he would have flat spotted both tires or even nosed it over!