One bit of lock keep required

Highly unlikely I appreciate, but I'm after a single component from a door lock keep. Take a look at the following image :

https://www.upvc-hardware.co.uk/images/medium/gu_clatch_dbolt_keep_MED.jpg. See the silver bit? That's the bit that catches the door when pushed closed. I need that silver bit (long story, but I've basicallly dropped it into a inaccesable place, so have no option, but to buy a new one).

Actually, the silver bit I need is for a Coldseal unit which you can see here : https://www.upvc-hardware.co.uk/kee...oller-1-deadbolt-one-piece-door-keep-514.html, but the principle is the same - its a silver piece and I expect they're all standard sizes. I could just buy that piece there - but its £35 and I can't see the logic in buying something for £35 when the piece I need is probably about £3.

Any help/ideas?

try a local locksmith,they may have old/spare keeps ? what about buying the unit in your 1st pic and taking the part you require off that ? its probably the same and it was only about £6 ?
the part you have lost in an inaccesable place,can you see where it is ? or is it that bad?