I don't think you can buy proper holsters for it here, at least, not at a worthwhile price. My friend who lives in the US carries a real one daily and just paid almost $150 for his one at Christmas.
Just need to wait for the next UK Tactical discount on Warrior kit. They have just had one for 20% off. Their holster is quite good, I bought one in a sale before getting a pistol, unfortunately it is too small for a Mk23.