Didn't realize how many people was actually missing these. Not to mention you have to order the whole unit. Cheaper on Amazon. Even cheaper is to use a cap from your air valve stem from your tire. I used this one with a hole in the middle. Little dab of glue. Done.
That is a good hack. Unfortunately for me, the passenger side doesn’t turn at all so I‘ll have to go the replacement route. I went with the $40 option from ebay.