How to install b43-firmware on arch without internet access?

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http://unix.stackexchange.com – I currently don't have wire internet access in the PC I'm trying to install arch to, but my other PC (win7) can access the internet just fine. I tried downloading the b43 package from the AUR and copy it with a pendrive but when I run makepkg -s --asroot it goes and tries to download the source from "http://www.lwfinger.com/b43-firmware/broadcom-wl-5.100.138.tar.bz2" which doesn't work since I still don't have internet access. I manually downloaded the source on my other pc but I guess I have to modify the PKGBUILD file to reflect this so instead of trying to fetch it online it looks in my lo (HowTos)