Don't really want to spend £20 plus as it's only for CX bike , so who do folks use ?
I've always used BETD, you might just sneak under £20 depending on the model. You could always try the shop you bought the bike from, they may be able to help too.
Edit, just remembered, Superstar do them too, much cheaper as well albeit their selection is more limited.
Why does it matter if it's just for a CX bike? Cheap hangers are cast and they do flex, not a great deal but it affects some hangers more than most. The flexing can cause issues shifting. Those such as BETD are fully CNC machined and are of a better quality and available post free too.
Try 925engineering.com on Ebay approx £ 12.50 posted.
I have used BETD for years, excellent quality and well machined
You can either have the best - North Shore Billet = £
or cheapest - Superstar = swiss cheese