Wife trying to drive wedge between son & me

My son has an Apple watch but my estranged wife (she cheated) was allowing him to also use her second IPhone. He was using it more than his watch and would delete the texts between us for privacy purposes. Wife found out and is refusing to allow son to get his own IPhone as planned for his upcoming birthday unless son and I apologize to her in person. Putting aside that I don’t think an apology from either of us is in order, I feel she’s dragging our son into our issues. Are there any recommended free or low cost resources for resolving this disagreement at the parent level? Such as a mediator. Wife already gave up on marriage counseling and we can’t afford it anyway as she’s been self-medicating with spending.