Source for those foam door hinge dust seals?

JDMopar said

It's seam sealer. They gooped it in there to keep the water that runs out of the cowl drain from running into the oversized bolt holes that were needed for door adjustment. If you look, you will find it on the back side of the inner half of the hinges also.

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I looked at an extra door I have and it is clearly seam sealer. The ones I took off the car were cut from white foam approximately 0.25" thick. They were cut perfectly to fit the hole. Appeared to be cut with a stamp. Definitely not cut with a razor or scissors. Strange.