Source for Steering Knuckle Seals

I posted this question on the Members Restorations forum and didn't get any takers, so I thought I'd ask it here too. I want to replace the white foam dust seals that are sandwiched between the steering knuckle and the front drum brake backing plate on my 71 Dart project. I have not been able to scare up a source for them anywhere online. I am thinking about trying to fabricate my own from sheet foam material if I can find a suitable material. Has anyone here done this? Where did you find the material to cut them from? Anyone know of a source for a ready-made seal? Any help here would be appreciated. TIA!

Jim