Windows 8.1: how to update Broadcom driver without using external drive

I am looking for a way to update a Broadcom driver without using BootCamp or external boot drive.

I have a Macbook pro mid-2012 (non-retina) and successfully had Windows 8.1 running on it, except it does not detect any ethernet and wifi devices.

I used Bootcamp through which I believe I got the latest Windows-support drivers and firmwares.

I do not have access to any external drive to build a boot drive and to any network which I might download softwares directly from a Windows partition. The entry point is the OS X partition.

Any help would be greatly appreciated.