Bleached tripe has little nutritional value for dogs. As Pam says it's the green tripe you want. Some info here
Green Tripe Site Index
I get a whole cow tripe for £2.50 straight from local butchers.. they slaughter there, not many do these days.
It's big - the last one I had was 3' x 2'. Cut it up into pieces, put in freezer bags. Day before I want it I drop bag in a bucket of cold water in my outbuilding to de-frost. Then just give a piece to each dog outside.