This is a set of files used for my daughters toy-horse, which was made by wood.
It consists of the stirrup itself, a little bracket to fix it in place along the sides and finally a sleeve to prevent the belt / strap from peeling-off its glue.

I printed it from PA-HT CF, which is Carbon-fiber polyamide (nylon CF) - but most likely other stuff, such as ASA or PETG will just work fine with several walls.

Assembly is easy, I used a strap from a cargo-fixing set and cut it to length. Then I folded each end in on the stirrup, BUT previously slid-on the sleeves. Then I used a glue-gun to glue it together flat and cut-off the excess glue at the sides. The I use a flat iron to melt it together better. Finally I added the sleeve close to the glued part and also secured it with hot-glue.
This prevents it from tearing apart from my daughter forcefully stepping onto it. (otherwise the glue separates, I tried it)
Be aware, the sleeve is not shown in the picture but only in a sketch.