The top part of my filter tank has a large crack in it and I need a new one. I really just need a top that is comparable, but will most likely have to buy the tank as a whole. The FSH 500 (500 sq ft) is no longer manufactured and I'm looking for another tank top that would be the same in size so I don't have to replace the whole unit. I'm trying to replace it at cheaper costs since I just replaced my backwash valve. Any help in comparable FSH 500 tanks would be helpful.