My mistake. I thought that the Treehawk had an octagon to round barrel. But I did find some photos of one.
Apparently there is a TC scope mount and base adaptor for the Tree Hawk but I don't know where to find one.
And at one time Kwik Site did make a scope mount for the Grey Hawk and Tree Hawk, part # KSM22198 "Kwik-Site Integral See-thru Blackpowder Mount and Ring Set, fit Gray Hawk, Tree Hawk, stainless $44", but not currently available on their website.