You may find some fruits are quite high in glucose (bananas, other tropical fruits, dates, cherries, sweet grapes to an extent).
Barley Malt Extract or Rice Malt Syrup is also excellent (can probably be found in your supermarket and/or local health food shop?). Not only are there some good minerals and vitamins but maltose = glucose + glucose disaccharide. Breaks down fairly readily (low metabolic load) but not really quickly. Basically all glucose, unlike table sugar (sucrose = glucose + fructose disaccharide).