For kydex, I’ve done business with David Brown of Buy Brown. Highly recommended. I’ve also received a Mashed Cat sheath that came with a knife from the exchange, and can vouch for quality. I’m sure others will be by soon with more options. Best of luck!
With kydex Buy Brown might be your best option as it is likely that David will have Chopweiler on his wall, and then pancake style gives you all the eyelets along both edges to attach stuff to it.
With leather this kind of stuff can be done.