I walked the Camino in the summer of 2007, and before I made it to St. Jean Pied-de-Port I spent a day and a night in Bayonne (nice town, by the way).
There is a large sporting goods store, but it's a good walk away from the train station (the tourist office folks speak English, and can provide him with a map). I bought a good poncho there, along with some biking gloves (I walked, but wore the gloves to protect my hands, as I used walking sticks), and one other item I can't remember at the moment.
St. Jean has a couple of shops for pilgrims, but it would probably be best to have what you need before you get there, as St. Jean is a fairly small town.
By the way, I spend a couple of days in Bordeaux before I hit Bayonne, and there's a good outdoor store there, where I got my trekking poles, bug repellent, and Nalgene water bottle.
The biggest mistake your father can make is packing too much, as I did. He shouldn't be carrying much more than 10KG of weight, including pack.
Also, keep in mind that Spain has good outdoor stores as well - he should be able to find one in Pamplona, and the Planeta Agua store in Logrono was helpful for me, since by that time on the Way I knew what I really needed and what to get rid of.
As you've noticed, this site isn't really geared towards the Camino. I recommend that you do a search on the following terms:
Confraternity of St. James - they offer good guidebooks and Camino info. Here is their site:
http://www.csj.org.uk/
Ivar Revke - he runs a good pilgrim website out of Santiago where your dad can meet and dialogue with pilgrims past, present, and future. The site is:
http://www.pilgrimage-to-santiago.com
Feel free to message me with further Camino questions - and Buen Camino to your dad!
