During my tour of Oz there were several times on gravel roads when front sus would've been good - what would be a good strong touring fork for the RT?
Unless I'm mistaken the Raven Tour uses a non-suspension correct fork. That means if you put even a moderate travel [80-100mm] fork on that bike the front end will get raised ~2" which will compromise the handling. At the very least I'd try it out before committing to buying a new fork.
If you aren't already doing so running a pair of 2.25" Marathon XRs at moderate pressure will absorb a lot of road shock and will float nicely on loose gravel. That might be a better option than a new suspension fork.