Do a Google search for the Bemis Color Direct Toilet Seat Kit. They have 94 colors plus white. It's about $50 but they have most manufacturers' discontinued colors and it's a good quality plastic seat. You can find it for a little less on the online auction sites and I believe someone on this site has mentioned before that The Home Depot carries it as well.
They don't specifically list Borg-Warner but you will receive a color chart with samples of all 94 colors. I'm sure you can find a match.