They're made of silicone, so they're pretty tough and durable, soft and stretchy. Just what you need in a severed finger. Right now they're selling for $12.95 CAD, you can pick what one you want: male finger or thumb, or female finger or thumb. Or all 4, for $39.95 CAD.
You can buy these bad boys here:
Set of all 4 Severed Fingers,