Firewall rubber boot for brake rod

[FLcustom10]

I need the brake rod boot that mounts to the firewall where the brake pedal rod goes through to the booster assembly. Everywhere I look it says it is discontinued by the manufacturer. That's a big hole that I have to do something about. Any ideas on where I could find one? No old trucks in the junk yards around here. Vehicles get scavenged and crushed within a few weeks of coming in.