Raymarine Raychart RC425 charts help please

[Prairie Chicken]

Our new boat has a RC425 plotter but no card or charts. I found a website which indicates the RC425 takes a 'Navchart' card with 'Classic' charts, but I don't know what a Navchart card is. I know the card slot on the plotter is larger than any card I'm familiar with. Is the data on the card, or does the card hold a SD card of some size?

We have the Med charts we need on a new Navionics Gold micro SD card from the plotter on our old boat but Navionics are telling us there is no economical way to convert back to the old 425 card. I'm still hoping there is some way around this without buying a new plotter.

Would anyone out there have any suggestions? Does anyone have Med charts on a Navchart card they no longer require? Or, has anyone found a work around to get the data from a new card onto an old card (once I find an old card)?

Any suggestions would be welcome.