Mammut doesn't have a monopoly per say, but the method in which they produce the slings kinda creates one... they actually weave the sling wider at specific points (12", 24", and 48" etc.) to allow for the stitching/bar tacks... that is to say one can't just whack off a specific length and sew it together. You might be able to purchase 24" runners from mammut unsewn and then get mammut (or someone else… I’m willing to bet Metolius would do it for you… let me know if you need a contact name) to sew what you are describing. I do believe the mammut rep posts on the page semi regularly (at least that is his avatar); perhaps you should pm him. Something I do often to get around this is to girth hitch 12" runners to the sewn runner on the cam... just clip the appropriate length and run... make sense? Hope this helps!