How about putting some Travertine exposures on the island (near the shop) or move the shop across the water closer to the actual Trav field now. Please, I'm not suggesting to move the Trav field to the island but add additional exposures there.
Way it is might as well just drag disk to delgarath then travel the distance needed to get to the shop on the isle from the Trav field.
Rwrr!!! Smaug Rwrr!!!