A4 envelopes

What kind of a post office doesn't sell envelopes larger than A5 size? Oh, oh, I know the answer to this: my local one. Postal prices have gone down, which is great - but not huge amounts of help if I can get an envelope to put everything in... Nor do our little supermarkets sell anything bigger than A5. I'm actually going to have to go into town and go to the Giant Supermarket That Sells Everything But Is Populated By A Million Screaming Children, aren't I? Just for an envelope. Bah.

(I would, by the way, like to reiterate that postal prices have gone down - I'm still a little in shock over the SNCF actually providing some customer service and fixing their fuck up, and now postal prices have gone down. I need little things like the complete absence of any useful envelopes to remind me what country I live in, given the sweeping changes that are apparently taking the nation by storm.)

ETA: The reputation of the village has been restored. For future reference, and in case anyone else is wondering where to buy A4 envelopes in France, try the tabac. Mine even sell them singly, so you don't have to buy many when you only want one. Success!