I haven’t needed the firewire port replaced on my XH-A1S, but I did need to have the port replaced on my XH-A1 twice. There’s a repair service here in Florida I used:
https://www.avrepair.com/
If I remember correctly, the price has around $250, but it’s been a few years. I also had the camera cleaned and serviced, so that was the total price. But you can probably ask the guy if he can still get parts and for an estimate. He seemed pretty good. His work was good and so was the turnaround time.
Hope this helps.
By the way, I’ve recently upgraded and will be selling my Canon’s soon.
Roger