SanDisk Extreme SSD Firmware R211m download for for MacBook and MacBook Pros based on NVidia MCP79 chipset

My optical drive on my MBP is dead. I’ve tried to convert the iso to a dmg and mount it on a USB drive, but Mac Os can’t find when booting with Alt pressed. I’m not going to buy an optical drive and burn a CD just for a (much needed) firmware update. What can I do ?