pin backs for fiber jewelry

[Polly]

The only shape we have is a rectangle (about twice the size of the bar pin).
What about using the "plastic canvas" stuff that people cross-stitch on?  I *think* there are some fairly small-holed ones that would be fairly easy to cut into specialized shapes, plus would make a great gluing surface.
You might even be able to use those fancy large (1.5", 2", etc.) paper punches to punch some common shapes, like hearts.

Anyone know a better product than the cross-stitch "plastic canvas"?  It's been a long time since I looked at much fiber art, and I wasn't looking at jewelry-related stuff then.

[fiberart3]

I am looking for backs which can be used behind various kinds of soft fiber pins.  They would ideally be hard plastic and available in various sizes and even  shapes.  I know they exist...just don't know where.