The displacer (rod) bearing is not a conventional gland, because that would cause too much friction. There is no foam involved. It is a close-fitting brass tube, fairly long to minimize the leakage. The rod must run absolutely freely in it.
The regenerators can be of almost any OPEN-cell foam or weave. Rigid foam is best but not essential. Air filters are often of suitable material - try an air-conditioning supplier. However, I have used flexible foams and even a plastic pan scrubber quite successfully.
Remember, you are using minute power, so cannot afford much leakage or any friction. The engine will run for an hour on an insulated mug of hot water, so the heat flow is very small. Worse, because this is an LTD engine, especially if to run on your hand, very little of the heat flow is converted into mechanical work.
An exhibitor once remarked "Don't ask how long it took to make it, ask how long it took to make it GO!" Good luck with minimizing friction, leakage and in getting the balance right!