There are a lot of different brands on Amazon and Ebay. Also at Music store sites. Most are guitar extensions or small straps. THey come in real leather and man-made faux leather. I don't remember the brand, but one offered a wide variety of brown, tan and black color leathers. Some with a star on the button and most plain. In Antique brass, or chrome silver.
It trimmed a couple down width wise, and used them for a while. Even made my own. I think they look much classier than a shoelace.
Eventually, I decided I preferred strap pins on the side of the heel.
Here's an Amazon link to the Calvery strap extensions, but they are currently unavailable.
Genuine Leather Acoustic Guitar Strap Button - Single Strap (Dark Brown with Gold Button) - by Cavalry Straps
https://smile.amazon.com/gp/product/B0716KDFSN/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1