you can still get them... in loads of places. We have some which are TV character-themed (Postman Pat, ANgelina, etc), and we got those from a local toy shop. Then, we also have some Disney ones from the Disney Store. Also, there are the Imaginetics things, which are similar - a board, with character magnets. We've got the Mr Men one (you can get these on Amazon).
Not sure but ds1 got given a postman pat book like that last year sometime. Have to confess though, that they still don't last long - they don't always peel back up perfectly (especially if the shape is complicated - an arm can easily get ripped off) - but it did last longer than normal stickers.
Can't tell you whether it's more or less wasteful than stickers, to be honest. You can get really quite cheap huge boxes of stickers at places like Woolies and I don't think the books would be that cheap (ours was a gift so I can't say for sure).
No, I realised that after I posted! Still don't know though. Depends how much the story gets read afterwards even without stickers (with ours we just got whiney tantrums about how much he wanted the stickers back for it, so the book was quietly "lost" after a while)
We have loads, many of which we've had since ds was 2, and he's 10 now! The main "name" seems to be Uniset. If you go somewhere like Mailorderexpress and just put the word "uniset" into the search box you'll see loads. In shops they're often on special stands that circle round IYSWIM.