My first choice for a pastel paper would have to be any decent hand-made watercolor paper
A very close second and, in some ways, also my first choice is Waterford Watercolor, Rough
After that; anything with plenty of tooth and strong enough to withstand some scraping and a lot of water and fixatives. (I tend to make a watercolor wash using pastels and a wet paint brush to create my initial background colors, layout and color scheme... after that, I always go over the top with fixatives - except in the final layer where I never use them)
Canson Me Tientes is great when I want to really force myself to go easy on the application of pastel and try to keep to a more traditional style of pastel painting with at least a bit of the original paper color showing through...