Custom fonts on PW1 update 5.6.1.1

Hi All. Sorry if this been answered already.

I had silent update of my PW1, it's now 5.6.1.1 and I lost my custom fonts :(

I'm very disappointed with that, because this was the only way to read Old Church Slavonic on Kindle.

What is the easiest way to get custom fonts back? Do I get it right, jailbreaking of this version requires opening device and soldering wires?

Thank you in advance!