You may be able to get a Don Hume for it:
H715-M W.C. [H715-M] - $28.45 : Don Hume Leathergoods, manufactures high quality leather and nylon goods. Model 19=Model 66
The link appears to list customizing the barrel length if they make the stock model for a 2.5-inch barrel.
Finding an IWB for a 4-inch may be tough otherwise.
Good luck with whatever you find!