The cheapest place I have found online is the American Diabetes Wholesale Company:
Diabetic Supplies Online - Diabetes Testing Supplies - American Diabetes Wholesale
They do charge for shipping, but if you spend $100 or more they have free shipping.
Actually, I prefer Pixy Stix, and my daughter uses Smarties candies--they both have basically the same ingredients as glucose tablets:
Dex4 Glucose Tablet Raspberry
Ingredients
Dextrose (Glucose), Cellulose Maltodextrin, Magnesium Stearate, Citric Acid, Natural and Artificial Flavor, Artificial Color"
PIXY STICKS
INGREDIENTS: Dextrose, Citric Acid, LESS THAN 2% OF: Artificial Flavors, Artificial Colors (Blue 2 Lake, Red 40 Lake, Yellow 6 Lake)
SMARTIES
INGREDIENTS: Dextrose, Citric Acid, Calcium Sterate, Artificial Flavors and Colors (FDC Red 40 Lake, Blue 1 Lake, Blue 2 Lake, Yellow 5 Lake, Yellow 6 Lake)