By far the cheapest Micro SD method : r/miniSNESmods
The SuperUFO as an import adapter – VideoGamePerfection.com
Memory Stick Micro SD Adapter for PSP | Hand Held Legend
Amazon.com: Over 23,500 games on 64GB SD card for Hyperkin Retron 5, Genesis/MD NES SNES Game Gear Master System GBA GBC GB Famicom Super Famicom Satellaview SG-1000 SC-3000, MANUALS, CHEATS, ARTWORK, Plug
By far the cheapest Micro SD method : r/miniSNESmods