Alex, what is the material? Those look cotton, not nylon but helps to know which.
This person on Etsy has a lot of variety
this round one looks similar: https://www.etsy.com/listing/167269676/4-strand-round-braid-paracord-leash?ref=related-3
These fleece ones look interesting.. you can totally design your own from colors to snaps!
I had braided cord for my horses, not dogs so no personal experience. Hopefully someone else here does.