Greaseworks had viton injector return line kits.
Injector return line kits
4 Cylinder Kit
5 Cylinder Kit
You can also buy the 1/8" hose in bulk, for $3/ft

They also have bulk viton and 30R9 hose:
Bulk Viton
Bulk 30R9

Also I've never put a viton o-ring on my tank screen. I have 25k miles of biodiesel use after cleaning the tank screen and replacing the o-ring. It hasn't started leaking yet, and that was three years ago. So I'd suggest a regular tank screen o-ring.

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