Hi Jean! If you're starting to have a go, I would suggest that you, perhaps, try simply using Rough Watercolour Paper to practice on; there is the slight problem of white spots, where the dry colour doesn't quite reach the bottom of the paper texture, but its good to practice on.
When and if you have had a go at this, then have a look at the SAA Shop again, and consider something like Hannemule or Clairefontaine Papers when you are ready for the next stage.
For a really effective portrait, try using one of the Velour Papers for a very soft effect.
As a stop gap until you feel confident enough to spend money on good pastel paper, have a look at your local art supplies shop where you should be able to get something cheap to work on; you should be able to get a pad with a variety of colours.
Good luck and very best wishes,
PA & RSC Wigan / Warrington / St Helens