Power Steering Cap

Hey everyone. I need a power steering cap. The PO took it off and lost it somewhere, and now I can't find one. I've tried a couple of junk yards, but most won't sell parts like this separately. I've also tried looking at O'Reilly, but they don't have anything close. Does anyone have one that they can part with, or know what else would work on this car? It's a '70 Plymouth Duster with a Slant 6. Let me know what you got. Thanks