I'm not familiar with a holster that serves dual-duty like you describe, although I'm sure somebody makes one.
I really like the Blackhawk SERPA CQC holsters, but don't have one anymore and can't tell you if it will allow for your extra barrel length to stick through...I think it will, but I would go check the holster in person before ordering one.
As far as your choice of firearm, as a Glock 35 owner I can tell you that I think you will be very pleased.
Good luck with your holster search and let us know what you turn up.
I don't make jokes, I just watch the government and report the facts. -Will Rogers
An appeaser is one who feeds a crocodile, hoping it will eat him last. -Winston Churchill