Yes.
Download it from a direct link - they can be found by googling it or may even be listed in another forum topic or on sites like iclarified. I wouldn't be surprised if someone even posts the direct link here - but either way you can find it quite easily.
Just download it and save it.
When you connect your iPhone just click on Shift and restore/update on PC or alt on mac and the browse to where the download is saved and click on it.
iTunes will then restore/update from that file.
Make sure you save the restore file on your hard disk as some people have problems with itunes extracting it on flash memory!