These are the type of brackets used in some bathroom cabinets at my mother's house. She wondered why one of the drawers has never opened smoothly. Upon inspection, brackets was never installed. I don't see anything indicating the cabinet maker, and the building contracto has passed away leaving no business behind. The house was built in Burton, MI (near Flint) in 1990.
I can't locate the piece anywhere I've searched locally. A picture of one of the brackets posted on your website looks to be extremely similar; close enough to work as it appears to me. Thank you for your help.