For a specialty item like this, you're not looking to sell it to the average person who wants a practical pen (like most of us are). They'll go buy a Parker with a plastic body. You're upcharging for the uniqueness; you could get hundreds of pounds if you write a good little story about the wood you used, and the tree it came from, and find the right buyer. I'm sure there are established pen stores you can contact to see if they'd be interested in selling such a piece for you. You'd get less, naturally, but your products would be getting in front of the right eyeballs to be sold.

Or, keep it, and have a truly unique pen as a status symbol 😊