There are pix of two Hoak rifles in Behold the Longrifle by by Chandler and Whisker, and a carved example in Behold the Longrifle Again by Whisker.
Kentucky Rifle Patchboxes Vol. 2 by Chandler & Whisker has pix of 3 patchboxes.
Kindig's Thoughts on the Ky Rifle has some info and pix of one rifle, and the Pennsylvania-
Kentucky Rifle by Kauffman has one.
Finally, the Frazier Museum in Louisville Ky has (had ?) a Hoak on display. Sorry for the quality of the pix, taken of a display case.
All the best
Paul