Maltrin M100 is a maltodextrin manufactured by Grain Processing Corporation (GPC). Looking at their website (below) I discovered there is sample request section. I requested a sample which they shipped, no questions asked. The sample is approx imately 600 grams so I18'm set for a while.
http://www.grainprocessing.com/food/maltodextrins-corn-syrup-solids.html