Mini Chart Cards?

[NavyWings]

I purchased a 2004 370 Express back in October. It was originally located in VA and I'm shipping it up to Michigan where I'll use it mostly on Lake St. Clair and Lake Erie. I've been searching for a new Mini Chart Card for the Lake St. Clair area with no luck. Even Furuno's site says "discontinued." Anyone know if there's either a vendor for these or is you can write charts to a blank card and use it? With cards seeming to be upwards of $200, I'm guessing my best option would be to upgrade to a new chartplotter? Recommendations? I currently have the Furuno GP-1850W and I'm leaning towards the Raymarine eS75 which seems like it will fit the spot well. Also with forward vision to switching over all the old electronics.

Would appreciate any insights.