New locks/ openers for double glazing

[Shedbuilder]

I've been asked to source some replacement openers/ locks for double-glazed windows. The owner of the windows is convinced they can replace them themselves with a screwdriver if I supply the replacement parts. They can't, at the moment, leave home for health reasons. Has anyone done this? Is there a particular supplier you'd recommend? Is there a massive choice: do I need a serial number or something? Thanks in advance.

They are easy to replace. If you search on Amazon for UPVC window handles you can buy them in multiples so they all have the same key.

Thanks!

@Gemma2019

They are easy to replace. If you search on Amazon for UPVC window handles you can buy them in multiples so they all have the same key.

I've looked and it's not handles I need, it's the kind of locking opener that comes on decent-quality UPVC double-glazing units. I've googled for replacement locks online but I'm not getting anything that looks like the original fitment. I'm going to have to go into a double-glazing place to find what I need. But thanks anyway!