I don't know where you could get a credential in Limoges, I'm afraid.
I would suggest that you make yourself a Pilgrim passport with some nice paper and card. Write all your details at the front, name, where from, where starting etc, and make some sort of chart for stamps to be stamped in. Once you get to St JPDP you will be able to obtain an official one, and meantime you will have a nice record of where you have stayed. When you come to ask for your compostela it will make no difference where your official record started.
Give our love to Flavignac pilgrim gite, and the nice girl who will come to collect your money. We stayed there in Oct/Sept 2008. See if you can work out the strange carving on the church opposite the refugio door. Nobody I asked seemed to know anything about it!