Just seen this. The groove doesn't worry me but a chip does. Might still be easily repaired these days but my techie fiends () will be better at answering that part. As for copying a mouthpiece from a blank, @rhysonsax is right about Pillinger, it's what they do. Dawkes used to (still?) have their own brand of mouthpieces from a blank (Windcraft?). There again, this will be about the same price as a new Selmer so why not save yourself the hassle.tiny chip
These are his new 3d printed mouthpieces which are printed in PA 12 (a nylon) on an HP multi jet fusion printer. That's a far better process than Syos are using. It's nice to hear that they are good.If you do want someone to try repairing the Selmer, Brad Behn has an excellent reputation. Don't think he's cheap though!
Otherwise, I can highly recommend Walter Grabner's new HiTech range. The S2MO (medium-open) is 100% my favourite ever clarinet mouthpiece. Not certain if he does one with the kind of tip opening you're looking for, but I'm sure he'd be happy to advise if you gave him a call. As it looks like you're in the US, it should also be easy to get a few from him on trial.