Both the PK-232 and the MFJ TNCs already have digipeater capability and don't need any additional eproms. Perhaps what you are looking for is a NETROM network node eprom. You might check the TAPR site for info. I haven't worked with NETROM stuff for a number of years. I don't recall seeing one for a PK-232. Most everyone used TNC-2 clones such as the MFJ units.
You may have to obtain the hex code and get someone to burn an eprom for you. I doubt that they are available for sale as off the shelf items.