Amazon.com: SanDisk - 400GB microSDXC UHS-I for Nintendo Switch : Video Games
Sandisk Extreme 400gb Micro SD on clearance at US Costco for $24.97. YMMV : r/retroid
Amazon.com: SanDisk Ultra 400GB MicroSD XC Class 10 A1 UHS-1 Mobile Memory Card up to 100MB/s Read Speed (SDSQUAR-400G-GN6MN) with Mini MemoryMarket MicroSD Memory Card Reader : Electronics
Sandisk's super-fast 400GB microSD is ready for 4K HDR video | Engadget