I started making my own longbows many years ago and went down the path of making my own wood shafts. Very labor intensive, but you're not limited to the common 11/32 or 23/64 diameters of commercial shafting. It's difficult to get spines over 70 lbs at 23/64 diameter, but by making your own, 3/8 or whatever diameter you need to get your spine is doable. I made mine from Fir and they were excellent shafts.
Just another option if you can't find what you need from suppliers...
