dont know how well it would work for a larger stick, like a quarter staff, but ash is a nice light hardwood that i liek for whacker sticks ( being any stick designed to whack someone or someting about the head and shoulders or anywhere else), i have a cane length ( well it was for me for awhile now its about 2 inches to short) baton made from it and a pair of 20 inch long batons.
In the one fight where i used the larger baton I am pretty dure i gave one of my attackers a compound fracture, but it was dark and i couldnt see to well, but it sure looked like it. and the cane/baton remained sound, without enough of a dent to see from a foot away.
but it might not work out for soemthign longer, liek a bo staff, or quarter staff.
but it is a thought.
as to where to get wood and ferrules, woods like ash, or other hardwoods, in poles, could probably be had at a specialty wood's shop, or they might tell you where to look, and ferrules can be had from a company called Nibco
( i remeber it to be nibco anyway) they dont sell ferruls but the do sell unthreaded brass pipe caps, thats what is the ferrule on my cane/baton. dont have a web URL for them tho.