The cards aren't board specific per se. They are merely loaded with the factory fonts for that board. I never had a Prizm 4, only 5.1. Is your Prizm 4 a 4gb micro SD? If so, just get the Prizm 5.1 card, format and put your files on there for Prizm 4.

I bought a bunch of 4gb micro sds so I can have different cards for the same saber. Light side cards, Dark side cards, etc. There are limitations to what size card you can buy, so you're safer buying from TCSS. The manual does say somewhere the maximum size card you can use in the board, but I don't recall what that is.

Tom