I made my own. Went to TAP Plastics near where I live and bought a 24"x24" sheet of starboard. Then bought a suction cup device off amazon (West Marine used to have one too) for $8. Out the door, I spent about $60. With the small size of the suction cup device I bought, it can fit on the lowest step of the hull and all the way aft, so it holds STRONG. Definitely makes a difference on my X-22 but still need more ballast or bodies in the boat to really surf well. Our ballast is stock, so we use my huge brothers as the extra ballast.
The suckgate pictured here is not mine but it's exactly what mine looks like. I also followed the spec sheet shown here, for the most part. For my money, this was the way to go. Accomplishes the same thing for a fraction of the price and it's even cooler when you make it yourself, of course! One warning, it doesn't float, so you have to attach it to a coiled lanyard and hook to boat. Hasn't fallen off yet but it will sink if it does.