In case this is helpful to someone in the future, I'm replying to my own post to report back on what I've found regarding rear lighting on the Vintage Cruiser (mine is a 2017 model).
I did some research and found that Stellar Lighting in Elkhart, IN supplies the 12 LED lamp OEM (https://www.stellar-lighting.com/1202632
) tail light, as well as the 40 LED tail/brake/turn light unit (https://www.stellar-lighting.com/1254372
) currently being sold on Amazon. According to the specs on Stellar's webpage the dimensions are identical. My impression is that the 40 LED unit is replacing the old 12 LED unit. BTW.. the 7-diget number in the URL is also the part number.
FYI... Steller also makes the center LED clearance light strip at the top rear of the Vintage Cruiser (https://www.stellar-lighting.com/2225283-R
SPECIFIC TO MY ORIGINAL QUESTION
It's interesting that you can buy these 40 LED units one at a time ($20.04) for less than buying two ($55.99) from the other seller at Amazon - and they both have free shipping.
I think that I'll go the easy route and buy a new pair the 40 LED lights since, although branded differently, they seem to be made by the same company, and I am sure that if I went with a replacement, the one on the other side would probably fail in a year or two.
THANK YOU TO EVERYONE WHO HELPED WITH THE RESEARCH ON THIS!