Hi Steve, and welcome to the Challenge.
This is where Google Maps is your very best friend. If you zoom in to Invergarry a plethora of accommodation at every conceivable price range becomes available to you.
This straightforward search produces five alternate places to stay, at varying price points.
For a lone walker, Craigard House looks very reasonable.
Of course, there will be some Challengers who will have stayed at individual places who can give you an accurate steer on the qualities of the accommodation, but in the meantime, take a little time and look at good ol' Google.
If you don't like the look of any of these, then there's also the campsite at Faichem