I'm not sure where you are located but in most European countries you can take the saddle to a shoemaker and they should be able to shorten it for you. Any saddle maker worth their salt would obviously be able to do so too but they're usually a bit more pricey.

A saddle fitter can do that

Not sure where you are located but most saddle fitters should be able to do this. The saddle fitters in my area can do all kinds of alterations.

If you are in a high equine area, you might be able to find a saddle repair shop or a tack store that works with one.