Richo, after 7 Caminos, including Le Puy twice, I'm still looking for the perfect rain gear.
For the Le Puy I'm also in the poncho brigade because of the strenuous nature at the beginning, the need for ventilation, and because it covers the pack as well (more reliable protection than a pack cover).
However, the weather will be getting quite cold towards the end of your trip. I found I had to go and buy a jacket one year by the time we reached Moissac (left Le Puy mid September). My poncho was the square type with studs on the sides because that was all I could find in Australia. When it was windy, cold and wet it was not enough. Water came in through the openings, wind blew it around (even when cinched at the waist with my twisted elastic clothes line!)
I think if I'd had an
Altus type poncho/raincoat I could have done without the jacket, provided I had long sleeved merino underneath. The
Altus is available online from Caminoteca (€44) and I don't think the freight to Australia is too much - the total cost is less than the Sea-to-Summit Ultrasil which is probably the best of those available here.
The downside of the
Altus is that the sleeves can become a sauna.
There is also the Ferrino Trekker available through Amazon US - don't know anything about them but gather it is similar to the
Altus.
The Packa also looks really good - that you would have to order from the US.
http://www.thepacka.com
You might need rain pants to go with it - or a rain kilt which won't sweat as much as rain pants. It looks very cool!
The alternative to getting one in Australia is to wait until you are in France - not sure what sports shops are in Le Puy (forum members will know) but the French are well equipped for walking and they probably have more suitable options for the conditions than here. Australian trekking shops are geared towards bush walking where hardy equipment is necessary. Most ponchos would get ripped to pieces by our scrubby vegetation. On the Le Puy there are lots of ups and downs but the land and vegetation is soft.