Spanish Cedar Tray Divider Help

[HailTheBrownLeaf]

Hey guys,

So my trays for my first Tupperdor are seasoned and all is well. However the white (I'm assuming it's like a foam) end thingie came off one of my tray dividers and now the divider slides around a lot.

Where can I get a little foam strip to replace the one on the end of that divider?? What are those little white things on the ends of a tray divider made out of anyways??