We know Zeus BTC, but more than buying spare parts, we seek to repair the ones we already have.
If you have technical knowledge about repairing any kinds of Electronic boards you don't need to find someone to instruct how to repair PMU If I were you hire a technician to teach you how to troubleshoot PMU circuits (Board Level repair). As you can see on the PMU most of the parts are electrolytic capacitors they are related to power if one of them is busted then there is an impact on power output same goes for other parts like busted coils, transistors, and resistors.
If you don't have technical knowledge board level then replacing the whole PMU is the easier one.