Designing Kitchens and Bathrooms - Glass Shower Door Drip Rail

I had a custom slate shower installed, and the person that installed it did not put a 1.5% grade on the shower curb inwards to drain the water back into the shower. It is flat, so a lot of water, despite having a shower door sweep on the bottom, leaks out of the shower and is now leaking downstairs.

I searched for a drip rail/sweep that had an extended drip rail to take it out over the curb into the shower but no luck. And redoing the curb is problematic and costly. Any ideas on either a large drip rail or any luck on maybe attaching a rubber seal onto the slate curb? Surely/hopefully I am not he 1st person who had a bad installer and a flat curb.

A sheet metal shop could probably bend you one out of stainless steel or aluminum.

If I had it made out of metal, then I would have limited ability to open/close the door as I need it to go all the way to the edge of the door. I was thinking in my mind there might be a rubber sweep that has an enlarged drip lid that might extend further than normal????

I have the same problem... Have you figured out any solutions... I was thinking of a custom drip rail extension as the only practicle option?