Uhhhh, Vanilla . . . it would help immensely to know if you are male or female, and which orifice (or orifices, plural) you are stuffing with toys to "be satisfied". Obviously a male toying anally need not be concerned with the depth issues we "vagin-istas" have to face.

On the other hand, knotting Akita anally is a tough job, as many experienced users here will be happy to tell you. His knot has more than two lobes, and presents quite a challenge, compared to the more rounded knots on Boxie and Ruff Jr.
So, are you
Double-Stuffing (2 toys into 1 opening) ? Or are you female, and doing
Double Penetration (2 opening with 1 toy in each) ? If it's the latter, then I'd suggest Timberwolf for your next toy. BUT . . . if it's the former, then I'd suggest you squish your 2 toys together tightly, and measure around the knots. Then order a toy that's close to that circumference measurement around the knot.
Your big concern when going up in toy size is not just girth, but length! Although you might be very stretchy near the opening you are toying, your capacity for girth deeper inside might not be as great. Also if you are female, there is always the length/depth issue to be concerned about. Akita is 2" thick in the shaft, with an even bigger, multi-lobed knot. After plenty of work, I managed to knot Akita, but only when I was riding him, and could use my weight to force him into the pocket behind my cervix, and stretch that pocket till it bumped into my pelvic bone and I ran out of room.
Needless to say, that process was not particularly comfortable OR exciting, so I gave Akita to a male friend, who could more easily handle his length and knot.