Basically, you can take Fyren's l4dmmo.sp on page 4 and replace the PrepSDKCall_SetSignature lines for AddUpgrade and RemoveUpgrade with the appropriate lines from the snippets I added, and then you'll be able to use the mod on a windows server.
PrepSDKCall_SetSignature(SDKLibrary_Server, "@_ZN13CTerrorPlayer13RemoveUpgradeE19SurvivorUpgradeType", 0);
PrepSDKCall_SetSignature(SDKLibrary_Server, "\x51\x53\x55\x8B***\x8B\xD9\x56\x8B\xCD\x83\xE1\x1F\xBE\x01\x00\x00\x00\x57\xD3\xE6\x8B\xFD\xC1\xFF\x05\x89***", 32);
to get RemoveUpgrade working. AddUpgrade is the same sort of thing.
Actually, I should just make this easy... Here's a modified l4dmmo.sp named l4dmmowin.sp that comments out everything that doesn't work (on windows, because nobody has found the signatures yet), adds giverandomupgrade, and has addupgrade and removeupgrade working for windows.
Remember to do "sm_cvar survivor_upgrades 1" as well to allow upgrades on the server if you're using this.