Polyurethane Casting System A60 Flexible Set gives a nice flexible rubber like cast with high tear strength.
Xencast PX60 Medium Flexible Polyurethane Resin - Easy Composites
LET'S RESIN Polyurethane Resin, 60oz 2 Part Casting
Semi Flexible Casting Polyurethane Resin (Shore A 90 ,A 60 Mixing Ratio 4:1)
PT Flex 60 Liquid Rubber Polytek Development Corp.
Polyurethane Casting Resin D80 Kit - /en
Polyurethane Casting Resin Flexible Kit A60 - /en
LET'S RESIN Polyurethane Resin, 60oz 2 Part Casting
Enduro Soft - 2 Part Liquid Polyurethane Casting Rubber - Durable, Rubber Casting Resin - Soft Rubber Feel (2 lb kit (32 oz kit))
Enduro SOFT - Soft Rubber Casting Resin - Simple Resin
Polyurethane Casting Resin D80 Kit - /en
ClearWater Epoxy Doming Flexible -Resin Drop