Where to find these? Answered

Does it have to be exactly that shape?

There exist metal clips, intended for holding hair.

For example, consider the images, found here,

https://duckduckgo.com/?q=metal+hair+clip&iar=imag...

the results of an image search for, "metal hair clip"

To me, these look similar to your clilp.

I do not know the exact name for the clip in your picture. It might be a, "u-clip", but that is just a guess.

By the way, the price someone wants for such a metal clip will vary a lot, depending on the intended use. As an example, a lot of the search results I found included pictures of tie clips (for clipping a tie to a shirt) and money clips (for clipping a wad of paper money to itself), and those are examples where I would expect the metal clip would be overpriced.

I am guessing metal clips intended for holding hair in place, will usually be priced much cheaper per unit.

i would search google for "metal clip on bookmark" and do a product search. but a bench vice and some light gauge steel with a few supporting tools could make one just as well and for alot cheaper than google will find for you