Amazon.com: GeeekPi 6Pack TXS0108E 8 Channel Logic Level Converter Bi-Directional High Speed Full Duplex Shifter 3.3V 5V for Arduino Raspberry Pi : Electronics
4-channel I2C-safe Bi-directional Logic Level Converter [BSS138] : ID 757 : $3.95 : Adafruit Industries, Unique & fun DIY electronics and kits
2/4/8 Channel Iic I2c Logic Level Converter Bi-directional Board Module 2 4 8 Way Dc 3.3v/5v With Pins For Arduino Raspberry Pi - Instrument Parts & Accessories - AliExpress
Bi-Directional Logic Level converter using MOSFET
A Quick Guide on Logic Level Shifting : 5 Steps (with Pictures) - Instructables
RETIRED - Using the Logic Level Converter - SparkFun Learn