3500 leaf spring insulators

[78 Bonanza]

Attempting to hunt down the leaf spring insulators for my 78 3500. Called all of the usual places, Classic Industries etc. and they don't carry them. Does anyone out there know where I can purchase some or perhaps some universal units. I'm not talking about the spacers at the top and bottom of the perches
but the plastic shims that were placed between the leaf springs to keep them from rubbing. Mine have the holes in the springs to hold them in place. Thanks in advance for any help. I can post pics if someone needs to know what they are.