You can find the wireless charging coil on ebay for around $12, used oddly enough (eg.
Nokia Lumia 920 QI Wireless Charging Coil 100 Original | eBay)
Or you could buy what I bought and change your phone colour while youre at it (or keep it the same):
NEW Yellow Housing Cover SIM Tray With Wifi Charging Port FOR Nokia Lumia 920 | eBay
for $16.
Both are pretty easy to replace, qi coil you just peel off the old one, then light up the new one and stick it down.
The housing you just swap the usb connector into the new housing (and maybe the headphone jack depending on your phone).
Edit: i assume youre out of warranty, otherwise go down that route