There are at least two diaper covers that have a drawstring around the tail for containment. I can appreaciate the situation of a baby crawling around picking things up off the floor.http://www.doggon.com/dog_incontinence.htmlhttp://www.samsdoghut.com/catalog_g3.html?catId=56269
On the idea of expressing the bowel, I wonder if you are focusing mainly on the area under the tail when you tried to express the bowel? That works for dogs. With a cat, the abdomen is so very pliable, you can place the palm of your hand on the abdomen and place your thumb and fingertips on the sides up high near the spine and squeeze and actually move the feces in the right direction. You can't do this with a dog very well, the abdomen is firmer and more structured. My cats are generally very tolerant when I want to squeeze their abdominal area for whatever reason.
Did the vet tell you about the possibility of fly strike with an incontinent outdoor cat? It's where a fly lays eggs in the skin where it is soiled or raw, and larvae hatch and go down into the skin. If you don't catch and treat it, it can even be fatal. The other problem I don't know if s/he mentioned is a risk of megacolon. I don't remember if that came up earlier when you were here. A cat with fecal incontinence can develop chronic constipation leading to an enlarged colon and further slowing of the bowel. It can require surgery. Things you can do to keep her regular include massaging the colon and expressing the bowel, adjusting the diet, using medication (lactulose syrup, Propulsid), pet enemas, soaking in warm water, and keeping her hydrated with sub-Q fluids. You probably don't have time for all that with a baby to care for. Giving lactulose syrup once a day is easy and takes little time, that would be a good choice when you don't have a lot of time, you might ask the vet about it.