Adafruit FT232H Breakout - General Purpose USB to GPIO, SPI, I2C [USB C & Stemma QT] : ID 2264 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Devantech USB to UART, I2C, SPI, serial adapter (USB-ISS) | Acroname
Yocto-SPI - USB to SPI adapter (TTL 3.3V or 5V), driver-free