If your gun is marked for the .32 New Police cartridge this is identical for all practical purposes to the .32 S&W Long, which the New Police cartridge was adapted from.
Acceptable alternate cartridges are .32 S&W, .32 Short Colt and .32 Long Colt. There is very little hazard you will find any of these three at your local gun shop, however as only the .32 S&W and .32 Short Colt are in production at all, and that extremely limited.
For anyone doubts what I have said, find an old S&W box for a .32 S&W Long chambered revolver, or an old (1940s-1960s) "Gun Digest" and read the list of acceptable alternative cartridges!
The .32 Long or Short Colt cartridges will swell badly as they are undersized by ca. .025", but they can then be reloaded the same as if they were .32 S&W Long. You can use the .32 S&W Long dies and shell-holder.