Find a fitter that can use a 5 stud balancer.
In all the years I've had wheels balanced they've never used the stud/bolt holes to mount it in their machine, it always uses the centre of the rim. 
Stud balancers are better as they match how it is on the car, not unknown for the centre hole to be marginally out, ot corrosion cause it not to sit centrally.
Never come across one
...then i guess no balance issues on yours...? They are not commonly used as they take longer to set up. Wims work on an accentric system with 3 or 4 for 3,4,or5 stud patterns, where as my guys have similar but work on a peg and hole system with every denominator for each makers stud pattern. So that might explane why they are not the default equipment at most tyre bays. Where as wim use nothing else i believe.
I have yet to have an accepable balance using the traditional cone balancer through the centre hole, which bares no relation to the centre of the wheel when fitted with the bolts! (relatively speaking of course)
...its the bolts that centre the wheel, so thats the referance to use for balancing. But usually only used if cone balance doesnt resolve the issue. Wim aside.
