(assuming good intent) I’ve had good luck with online secondhand marketplaces. I know my sizes in my preferred brands.
I’ve had the best luck with shoes–my favorite brand only has a few base models and doesn’t take returns once the shoe’s been worn outside. So, it’s easy to search for, say, [brand] size 6.5 loafer and be certain they’ll fit like my other size 6.5 loafers.