An inline check valve in any toilet discharge line is a BAD idea because it can get clogged up with waste, TP, and mineral buildup (if your toilet uses sea water).
If your toilet uses sea water, the only solution is frequent joker valve replacement. You can make sure that the water running back to the bowl is clean by adding a couple of beer cups of water from the sink after solids--which you should be doing AHEAD of solids anyway.
If your toilet is one designed to use onboard pressurized fresh water, you can replace the flush button with one that has 3 flush options--water in ahead of use, dry flush, and the same simultaneous water in/bowl contents out that you have with the single button.
--Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein