I very much doubt you will find one there to hire. Revolutions, the Morgan dealer at Perth is probably your nearest
http://www.revolutions.uk.com/revolutions.htmlAlso, there is CaledonianClassic Car Hire but they are further away down north of Edinburgh
http://www.caledonianclassics.co.uk/location.asp but I suppose either could you mean you can take in a nice scenic drive up to the Orkneys.
No knowledge of either but others may have experience of them. Other people onTM seem to speak highly of Revolutions on here.