Marinette Yachts has the tracks that would fit.
I do know someone who replaced their handrails with a system similar to what you posted. Looks pretty good. I have no idea how to check the water tank either. All I know is that my water is clear coming out of it. There is a drain plug on the bottom of the keel for it though. My boat didn't have a swim platform either. I do know a guy that cut his in half.