The Dr. Ishmael can be found on the second floor of the Clothing Store and purchased for 420 Bucks. Purchasing this hat will allow you to wear this hat only in Adopt Me!, unless you buy this item from the Roblox Catalog.
The description of this item on the Roblox Catalog reads
"He's got a PhD in being OVAR 9000!!!! He got it at Oxford...."