If you find that you are in need of creating your own subwoofer cable, you can do it through Home Depot with a few items.
First, you need a compression tool. Check out this one from Klein.
Second, you need a RCA male connector. Home Depot only has one option, and here it is.
Third, you need wire. Here’s in-wall rated 14-gage in case you are routing the wire through your walls.
I found that I needed a solution when I had surround sound installed because the receiver end of the wire was not capped or terminated and I had no way to attach the wire to my receiver to utilize the subwoofer. The above tool and connector worked perfectly. Best Buy did not have any option for me, and the people at Home Depot did not know what to do. I had to figure it out on my own. Now, I hope you have an easy solution. Knowledge is power. Good luck!