Whereabouts are you visiting? We live in the Dordogne. There are no brands here of pre-packaged stuff like Nutriment or Natural Instinct but the supermarkets sell "viande pour animaux" which is off-cuts of meat. You can find it in the chilled meat section. It varies in price though from about 1.99 euro a kilo to 3.50 a kilo depending on which supermarket you use. We also buy "abats". The French are generally keen on offal so supermarkets usually sell kidneys, liver, hearts etc pre-packed. Our local Intermarche usually has at least one of them on special offer, so we stock up when they're a good price, anything from 1 euro a kilo up. You can buy chicken wings fairly cheaply too.
Also, if you are buying things for youself at a butcher's, you can ask for the "dechets". Our butcher will empty the contents of his meat waste bin into a bag for us. it takes a bit of sorting though to remove string and any particularly fatty bits but as it is free!
I'm afraid DIY is the only way to do it here though.
