E bay does have a lot of guys advertising pen blanks. If you put that in your search you will find thousands..
Other alternatives are local joiner shops, I went knocking on doors quite a few years ago and made some new friends doing it, offer to make them some pens in return for free off cuts you will be supprised what you will get.
Search in google for wood suppliers as well.
Another one is kitchen fitters, why? Well some of them will have fitted Corian work tops, another good material for turning.
What I'm saying is don't limit yourself to e bay as you will find them much dearer than other suppliers, that's down to e bay charges. Some of the suppliers on e bay also have there own website.
If you find a supplier on e bay, search google, very often you will find them and get them cheaper again.