Although I haven't been very succesful in getting some pop-up books, I have managed to get some pop-up cards.

They are quite cute - and you can buy small ones for £1.49 - rather than a bigger one of the same design for £4.49.

Here are some of the  designs - 'Treasure' by Up with Paper -

www.upwithpaper.com

As with most pop up structures, there are quite simple structures behind the mechanics.

Some are really just cuts and folds that make things stand out at different heights - something which could be easier replicated.

Info on the cards:

It seems they do a lot of pop up cards, stationary and books.

There is a lovely one - Barnacle Carnival with a carousel:
http://www.upwithpaper.com/products/books/everyday/jjp105-barnacle-carnival

And, as I mentioned earlier - stationary!...

http://www.upwithpaper.com/products/stationary/luxdesktop-notes/ev/dn012-fox

Just bought some more pop up cards from www.santoropopup.com too.

Again, using simple, but effective use of card, cutting and slots to create moving and 3D cards.