Not even sure how to describe the font to help my search. This is individual alphabet set, client would like to match to add more letters to their collection. But I haven’t been able to match the font with the 3D bevel…unless it was done separately.
I believe that is a Gemini Pronto Changeable Letter. It is a pre-made product by Gemini Sign Products. They refer to the font as “AD.”
They do not sell direct (though some companies sell online using a variant of their name).
They should be available to order through most sign companies.