I used to be able to pick up 10 packs of blank cards for making my own cards from dollar store type places for £1 but then I noticed the packs started to go down to 5 packs, and now there's just 3 in them! They're not worth it anymore from there it seems. I can buy the finished pieces for that. Where do you buy packs of blank cards from?
You can always look around online. I live in the US sho I don't know of any That'd be near you... So that's the best advice I can give.
I think there are some of the printing agencies that can do that for you. All you have to do is give them specific dimensions. And they can cut the mold with that specific one. You can also go with the standard dimension that usually found in the print companies. So with that you can get the proper cut as well. I'd recommend with that option if you're planning for something like that.