Permalink / 301 Redirect / Folder Name problem

Here’s my dillema: The client had a previous static site with a WordPress blog installed in the /blog/ directory of the root.

I migrated the client site to a full WordPress CMS site, with the WordPress files in a /temp/ directory and a redirect from the root so that the user gets the impression the site is located in the root directory.

The client wanted to maintain the integrity of her old blog posts, which were of the structure https://www.domain.com/blog/post-name because that site was in the /blog/ directory.

I added WordPress permalinks with the structure of /blog/%postname% to force the new post URL’s to be in the same structure as the old site, thus redirecting those post URL’s to the correct spot on the current site.

HERE’S THE PROBLEM
Users used to vist the site at https://www.domain.com/blog WITHOUT a trailing backslash, as that was a directory and Apache servers handle that request as if it were a directory even though there is no trailing slash. Trying to visit the current site without the trailing slash dumps the user into the /temp/ directory and a 404 error.

Is there a way, with 301 redirects or some other way, to solve this dillema? The client feels she will miss alot of traffic generated by old links, and I agree that she will.

Your suggestions are appreciated.

Thanks!