Click on 'Help & Contact' at the top of your page then 'Didn't receive the item' and follow prompts.

There is no need to contact ebay to open a dispute.

How and when did you pay for the item?  Once we know that there is sure to be someone around who can tell you how to proceed.

Is it the lock from the UK? If so it is being sent by GSP which is notoriously slow, I would give it 5 weeks before doing anything. GSP items have tracking so have you checked that to see where it is? 

It is very easy to open a dispute through ebay but you are probably being a bit previous,  ebay's number etc are there under help and contact, hardly hidden.

11 year customer looks like have made the final purchase !!

I'm sure eBay will miss your 20 purchases per year.

What everybody else said.

You've had an item not arrive and you are going to give up on eBay? How is it ebays fault the item hasn't arrived? I know they can be blamed for a lot of things but an item not arriving isn't one of them.

Follow the good advice by the other posters. 

I wish the OP would come back and tell us if they actually paid or not.

Cos that lock was re-listed 2 days later, and the OP is still waiting for delivery