You'll have to go to your local friendly upholstery shop I think. At least that's what I did.
I took along a regular (wrong size) Uncle Mikes holster as an example, and the pistol, (mine was scoped), and asked what they could do.
They said to leave the pistol and the sample and give him a week or so. He called the following week, and presto! It was perfect and very affordable. He stole the belt loop from the UM holster, and matched the material for the rest of the holster.