Between us, my garage and I have lost the keys to my 907. I still hope they'll turn up, but if they don't, is there a way of identifying and re-ordering the correct key, or do I need to start looking for a locksmith?

I think you are going to need a new or second hand lock set for this..........look on the bright side if it was a new Ducati then you would be looking at having to spend a huge wedge of money on a bundle of new electronics

Do you have lost both the keys?
Do you still have that bit of rubber which held the original keys? On that rubber there is a 4 digit number which allows to have the right keys.
Howewer, a good craftsman can create the keys from your locks.
Do you need to bring him one of the locks (i.e. the helmet holder) and he can make some new keys.

No matter, I hope you'll find your keys
Ciao

Its very hard to find anymore unused key blanks(base of key) to many older Ducati modells.... Making key from base is very simple...

When I got my 750 Sport it only had one key. I got blanks for a company called Keys4Classics http://keys4classics.com/html/Ducati_80s.html The blanks arrived promptly and were correct.

Pay attention. The '92 and '93 MY 907 DON'T have the same keys.
So, you need to know what it's the right MY.
The one with the lock also on the fuel cap is the newer one (FIAT Uno keys).
If it's the first one (no lock on the fuel cap or lock with key different by the ignition one) it needs the Zadi 10 key.
Ciao

Thanks for all the input guys, this is just what I was hoping for.

However,

The keys turned up today at the garage, down the back of someone's toolbox. Phew!!

So, you have a good chance to do some copies .
Ciao