The balancer removal bolts are ¼”- 28 threads per inch. The length depends on the puller and thickness of washer’* used, 2 ¾” to 3 ¼”. Local hard ware store should have these bolts for .50c each. The problem is the threaded part is over one inch long so be careful not to thread them in to far.
I have found a good source for balancer removal bolts that only have 7 threads on the end so you will not damage the back side of balancer.
This link has a picture of these NAS bolts for the balancer removal.
Any aircraft surplus store should sell these for $1.00 each.