In most towns and places in Mustang you can rent a horse or mule for your onward journey. The horse can carry you or your baggage. Ther horses in use here are incredibly sure-footed and quite used to novices.
A horse comes with a helper of driver.
Cost varies, but count on 5-800 per normal walking day routine.
Some hotels keep prices of such services on ther menu.
The flight to and from Jomson (-Pokhara) lasts only 20 minutes or so, bust surely is in the top league of the world's most spectacular flights.
You fly in from Pokhara early in the morning. After the strong northerly winds pick up at Jomsom airport about 11-12 pm no flights will take off from Pokhara.
The flights cross near the Poon Hill area just south of Hiunchuli/Annapurna South face and fly up the Kali Gandaki gorge (world's deepest, with towering 8000-metres Annapurna South and Annapurna I on your right side and Dhaulagiri on your left). The flight path is straight over the Kali Gandaki river, and quite low as you near Jomsom. You may see the villages of Tukche, Marpha and Syang on your left as you approach the runway. At about 60 dollars each way it's worth just the flight. I'm not sure if it's worth cutting off 4-5 nice hiking days, but if you're short on time, do it feeling good about it!
If you are planning to go to Jomsom in the Kali Gandaki - for the Muktinath pilgrimage trail or as part of the Circle Annapurna or Upper Mustang treks - ensure you add a buffer day to accomodate delays.
Delays are very common, and cancellations are mainly due to unfavourable weather. There may be fog in Pokhara or cloudy or windy in Jomsom. After you have done this, perhaps the world's most spectacular scheduled flight, you will appreciate a certain caution on part of the airlines that fly in here.
So do this: plan for an extra day's wait at both the Pokhara and the Jomson end. Have an alternative plan of things-to-do-if-flight-is-cancelled. Do not depend on having to reach Kathmandu or other places in Nepal apart from Pokhara the day you plan to fly out of Jomsom.
And - always assure to reconfirm your ticket!