What to do about a new seat ? Not the top cover it's fine. The bottom (plastic) part of the seat. It has many cracks. It's crushing the air filter box.
I searched for the seat fix . cant find it . Do you what the thread was ?Rookie, you will have a tough time finding a used one even on ebay that isn't close to the cost of new. The 800 seat bottom sits up high on plastic "feet" for lack of a better term. With age and your weight bouncing down they walk off the side of the frame rails and crack the pan. If you search, there is a fix with small angle pieces on the frame rails to stop this and keep you from messing up the air box, throttle body and plastics. You may be able to repair the old seat pan and fix the rails and get by but even if you get a new seat it will be in the same shape quickly unless you add the rail pieces.
Partzilla is about the best for new at around $217.
Is your suspension sagging?? Can't tell from the picture... need it to "scale"!