A few guys have separated the modem file into a tarball (I end up doing it all the time for the L900, L720, and M919). As long as someone has the MD5 tarball for their device it's easy to make one if they have access to a Linux terminal. Which build modem are you trying to flash in Odin?
By the way, odin is what Samsung devices use to load new firmwares. There's no fast boot commands you can use to flash as I haven't seen any kind of "bootloader" with fast boot command capabilities on any Galaxy devices (or any Samsung devices for that matter minus the Nexus).
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