Haven't tried this myself but when I was doing my research for this website, I read of several people that have had luck removing cat urine odor from leather but usually not the stain.

This is how they did it: Use an aerosol mister or a sprayer that you can adjust to the mist setting, and spray the area soiled lightly with the recipe. Then blot the excess off with a paper towel. Spray again and blot until the area has been saturated with the recipe. Let dry throughly before using the leather item.

They did say that the stain from the urine usually was still there and in some cases, it enlarged the stain. Almost all said the odor was bearable or gone. If you have to face the option of throwing the soiled item out or replacing it, I guess it makes sense to try it.

And of course check for color-fastness first, as most leather dyes are soluble and some of the dye might be removed with the blotting.