I SHOULD have grabbed the entire Gardeners Choice mower but chose just to remove the starter.
I agree they should be sold as a kit. Maybe ask the seller of the starter if they could add a cup as well?
This is why it is a waste of time buying any of the impact starters I see on Ebay as you need the matching cup as well as the special cup washer. They always just list the starter.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!