This will sound crazy, but try the gryphon. The shaft is long and thick, a good two inches that gets a little wider right before the knot! Luckily, it tapers slowly, is easy to take, and is really good for stretching. The shaft before the knot is actually about seven inches, but you don't need to take it all to get a nice stretch.
I don't own the following toys, but they look like they might help. The Trumpet
tapers, too, but it gets a lot wider starting at one inch and going all the way up to three. The only problem is that it has about eight inches usable. Titan
is nice and thick, too, though it does not taper like gryphon does so it will be harder to initially take. The head is two inches, though the shaft is a little smaller. Oscar or Lucas might be worth a try as well. Lucas is about 2 inches wide and it looks to be about 5 inches usable. Oskar is 2.5 inches wide with what looks to be six inches usable.