Help for 11 year old greyhound with bowel incontinence?

I am looking for something to add to his food to make his faeces a bit firmer, he doesn't have diarrhoea but as this mostly happens when he is asleep it's a nightmare to come through to every morning. He sleeps inside, and please don't suggest I let him sleep outside (won't happen). I am feeding him Bakers complete and because he won't eat just dry food I mix in tinned food as well. One website suggested pumpkin seeds - have you any suggestions?