Your RV probably has a Velvac mirror.
https://www.velvac.com/products/mirrors/shop-rv-mirrors
Select Ford, then Econoline Vans & Cutaways. If you have to replace the entire mirror and arm, be prepared for sticker shock.
They do have some glass replacement kits, but not sure if they still have that style.
But I would call them to confirm what your options are going to be.
Headquarters and Sales:
Toll Free: 800.783.8871
Phone: 262.786.0700
Fax: 262.786.4101