How can I post a couple of lithium ion batteries within the Uk?

I have a couple of camera batteries that i was going to list on Ebay, they are new, unused lithium 1900mah (13.7wh each). It occurred to me today though that the Royal Mail no longer allow the shipping of batteries on their own. I have checked the prohibited item list for my 'go to' courier firm (Parcel2Go) and they won't accept them either.
So, do I need to bundle them together with some random electrical item? Can anybody tell me how one can post a couple of batteries anymore? Thanks in advance for any advice, it is much appreciated.