We used J-Link with a J-Flash SPI license. https://www.segger.com/products/debug-probes/j-link/tools/j-flash-spi/ https://www.segger.com/products/debug-probes/j

We used J-Link with a J-Flash SPI license. https://www.segger.com/products/debug-probes/j-link/tools/j-flash-spi/ https://www.segger.com/products/debug-probes/j-link/tools/j-... Any SPI flash programmer should work though. The protocol is simple enough that you could even implement it with an arduino if you really needed too.