Pre USRAC red rubber pads appear to be pretty hard to come by. It is just dented on one corner, otherwise great shape.
The question is, can you live with it the way it is? You are not likely going to find an original WRA pad. Contrary to what some think, there was/is not a company making these:
Correct me if I'm wrong. I'd do like pal suggested and replace it, if it bothers you that much. The best replacement would be a red pachmayr. You could always keep an eye out on ebay and maybe one will pop up, but not likely. Good luck with it..