Thanks to J. Joey Smith for this Frugal Baby Tip!
What I do is use recycled Target brand soft cloth wipes (which, after using once, I run through the wash with my diapers) as a diaper liner. You just stick the square in your diaper over the cloth and it catches the poo. I pull it off and either flush the whole thing (which may or may not be good for my plumbing and/or the environment), or I just drop the poo in the toilet, off the liner.
Another idea, which I am going to try after I run out of wipes to recycle over and over (they last through several washes) is squares of flannel cut with pinking shears. You can get flannel as cheap as $1/yard at the fabric store, and each yard makes about 20+ wipes/liners. The poo
will come off the liner much easier than it would off of a diaper. I've been researching the many handy uses of flannel. (Also cleans silver nicely!)
In any case, what you need is a liner of some sort, so you can pull the poo out. They make flushable rice paper liners, too, which I've never used.