Engine miss when using power brake

While fooling with it, you can buy an inline carbon filter for that vacuum hose which is supposed to keep gas fumes from getting to the booster, in HELP shelves at auto parts. But, I put one on my 65 Chrysler and still got a hole in the rubber diaphragm, right where the vacuum port is. The rubber was hard and cracked there, but soft everywhere else. Worst thing is I couldn't find anywhere to buy a replacement diaphragm or just its molded rubber. Booster Dewey must have a source since he rebuilds them. The Midland-Ross type (post 1) are easy to take apart with the V-ring. The Bendix type (bent tabs) are harder (I haven't). There is a check valve where the hose connects, which is supposed to stop gas fumes. Next pass, I'll add a 2nd in-line check valve.