I am lucky in that the Hobby Shop (hour away) I get to visit (Hayes Hobby House in Fayetteville, NC) has been in business over 40 years. The owners have Peck Polymer's Jap Tissue on hand.
I have also picked up some of Campbell's Jap Tissue.
On the video from Robin's View about using jap Tissue, I *think* one method of shrinkiing is spritzing Isopropyl alcohol on it. I'll have to watch that video again!
