I have one of the older American Standard elongated Champion toilets in the orthopedic height that lately has started to refill the tank frequently. Late at night it would get a bit annoying. It also would "slip" on occasion when you operated the flush handle... nothing would happen. You'd try again and maybe it'd flush, maybe it'd slip. Well, it was getting to be bothersome.
Now any normal toilet I'd correct the refill problem by getting another flapper.... plus clean the outlet where it seats just to be sure it could form a good seal. But the Champion has a unique mechanism with a little tower that would rise up over a thin gasket when you operated the lever, allowing the water to run into the toilet bowl. When you let go of the handle, the tower would drop back down and reseal itself around that gasket. Well, my gasket had a zit. I slid a needle into the side of it and some water squirt out.... just a few drops but the shape of the aneurism was enough to keep it from seating. Looking at Home Cheapo and Blows was a waste of time when I looked for a new gasket. I ended up finding one at a little hole in the wall plumbing supply place (been in business for 65 years).
Unfortunately, it didn't solve the problem. I moved on to plan B, which was to replace the entire flush valve mechanism. The kind I had was problematic for American Standard and they had redesigned the valve completely. The new style valve could replace the older one; no sweat.
But then I asked for a tank to bowl gasket. Oops. No could find. Couldn't even find the part number. The lady at the hole in the wall supply house recommended another dealer. I went over there and sure enough, they had the new valve but not the gasket. He didn't know the part number either. He called his factory rep. The rep happened to have one available and miracle of miracles, it was a warranty item. It would be free. I could pick it up the next day. So then I asked, if the gasket is free, what about the valve? He called the rep back.
Heh heh... both were free. And the gasket kit also included new nuts and bolts for connecting the tank to the bowl. I didn't have to lay out a penny.
This morning I pulled the tank and swapped out the valve along with the bolts and nuts. It works, pardon the pun, like a champ. No leaks on my first try. Life is good.