Congrats on the PRS-300! Great size and screen.
If you do look for the part, here is some info: The site is
https://servicesales.sel.sony.com/ec.../web/index.jsp. Enter part
A1362416A in the search box and select Part Number from the drop down box next to it. The cost is $36 plus tax/shipping.
It's nice to have a backup!