I stumbled across these devices last week when looking at some ESP32 boards. Yes, 8 whopping megabytes of pseudo-static ram in a little soic 8 package using SPI/QSPI for less than a USD.
Seems there's a few companies making these devices, but they seem to be obscure Chinese and Taiwanese companies.
The ESP32 can map these devices into its memory map - unfortunately, most other micros can only use it as a spi peripheral - ie the 8MB of ram does not appear as 'normal' memory.
 I should note that my relationship with Electrodragon is purely as a satisfied customer and post the link as where to get these parts and for the link to the datasheet. The likes of Digikey and Mouser don't seem to stock these parts.