In my area, good mechanics are very hard to come by...Mobile mechanics, even harder. We have a two week wait almost every time we bring a truck into the shop. It wouldn't be hard to build a good list of tree service clients here.
See if there is a local arborist's association in your area and join it.. Go to their meetings and let them know you exist.
Find out where the local Utility tree service contractors are staging their equipment and go talk to the General Foreman one morning.
Act like your customers are a top priority and make yourself available when they need you for emergency work. Have a couple spare chipper tires mounted on wheels on hand and know how to repair hydraulic hoses.
If you can repair stuff really quickly the cost shouldn't be a real issue, within reason, of course.
Good Luck!
