Suggestions for antenna for FM verticals :
https://www.sirioantenna.com/index.php?main_page=product_info&cPath=48_45&products_id=378
Here is a better one:
https://fmbroadcastantenna.com/6meter.html
I feel it is a Sirio 827 10m modified by Norwalk Electronics. Either Way it works great. I have the Sirio 827 for 10m FM Repeaters.
MFJ/CrushCraft also makes one that works well that I have used for 6:
https://mfjenterprises.com/collections/cushcraft/products/ar-6