Chain and Keys
I found this "Albert Bronze Pocket Watch Fob Chain 021" on eBay for 8 quid:
The picture makes it look a lot better than it actually is, but it will do for me.
After removing the locket piece and adjusting the chain I added a couple of keys.
Although we never see the War Doctor's Tardis key, I thought he'd have an 8th Doctor key
and maybe a spare - you never know if you might lose one in a war zone :)

original

my chain and a couple of Tardis keys
Lighting is a real problem here - the photo of my chain and keys looks very brassy, but it actually looks
darker. The left-hand photo of the actual costume makes it look very dark - who knows, unless you've seen it in real life.