The ED64 Plus is a solution for using MicroSD card on the cartridge slot of the Nintendo 64.
I like the modern memory card solutions which use cheap media such as CF, SD, MicroSD, etc…
Information:
http://micro-64.com/features/ed64plus.shtml
https://ed64p.com/DOWNLOAD/DL.html
https://www.reddit.com/r/n64/comments/9h56ho/ed64_plus_working_with_custom_firmware_pretty/