If yu have a finger mate on your ring now, in order to get it over your knuckles, then
sizing balls at 4 and 8 (in the circle as like a clock) are the idea solution. A good jeweler should only charge you around $75 dollars and it will keep you stone centered
rather than slipping sideways.
Worked for me!
Unless there was any special process needed for a finger mate ring, the cost of getting the sizing balls should be much cheaper. My husband's jeweler put sizing balls in 3 of my rings and resized a 4th, all for $50.