Lexar High Performance 64GB MicroSD XC Memory Card 633x UHS-I Class 10 for Samsung Galaxy S8 S9 S10 PLUS + S10e with Mini MemoryMarket MicroSD Memory Card reader - Walmart.com
Here are the best microSD cards for the Samsung Galaxy S9 & S9+
Amazon.com: One Single SIM Micro SD Card Tray Holder Slot Replacement w/Eject Pin for Samsung Galaxy S9 Plus SM-G965U : Cell Phones & Accessories
MicroSDHC EVO Plus Memory Card w/ Adapter 32GB (2017 Model) Memory & Storage - MB-MC32GA/AM | Samsung US
Amazon.com: SanDisk 128GB Micro Extreme Memory Card works with Samsung Galaxy S9, S9 Plus, S8, S8+, S7, S7 Edge Cell Phones (SDSQXAA-128G-GN6MN)Bundle with (1) Everything But Stromboli MicroSDXC & SD Card Reader :
S9 Plus Case +Battery +EnviroSensor +Memory ++ - i-BLADES
Top things you need to know about the Samsung Galaxy S9's SD card slot | Android Central
Amazon.com: Samsung Pro Plus 256GB MicroSD Class 10 UHS-I Memory Card for Samsung Galaxy S20 FE 5G, S20 Ultra, S20, S20+, S10, S9 Phone - MB-MD256KA Bundle with Everything But Stromboli Micro
Amazon.com: Sandisk 32GB Extreme Pro 4K Memory Card works with Samsung Galaxy S9, S9+, S8, S8 Plus, Note 8, S7, S7 Edge - UHS-1 V30 Micro (SDSQXCG-032G-GN6MA) with Everything But Stromboli (TM)
Samsung S9 & S9 Plus || How To Use Both 2 SIM With SD CARD with Hybrid SIM Slot Adapter in S9&S9+ - YouTube