You probably need to go to a Micheal's, AC Moore type of store that carries the Wilton products. I've never seen meringue(sp) in the grocery store. Wal-Mart also carries it.
As far as sweet icing is concerned, I use 1/3 each of vanilla, almond and butter flavoring in my icing and everyone raves about it!
Leslie
Try this buttercream:
6 cups confectioners sugar
1/2 teaspoon salt
1 teaspoon vanilla extract
add and whip at low speed:
3/4 cup boiling water whip until smooth and cool add 2 3/4 vegatable shortening and 1 1/2 slightly chilled butter cut into 1 inch pieces increase the speed to medium-high whip until light and fluffy doubled in volume 10 to 20 min. yield 9 1/2 cups. hope you like it.
They sell meringuepowder at some grocery store but.. it not in the food section. It's usually in the section that has baking sheets and pans. I know Meijer has a Wilton section back in there and they have not only meringue powder, but colors and frosting and flavoring,etc.
Disovling a dash of salt in the water you use for your icing can help cut down on the sweetness some. 
I make my buttercream with 1/2c shortening, 1/2c butter, I add vanilla and then I add less then the recommended amount of powdered sugar, it's less sweet that way. The other way is just too sweet, and i find that I get a lot of comments that it's so good, and not too rich or sweet like the others. Hope this helps. I go by the Wilton buttercream icing recipe, I just use less sugar.
I use salt and a few drops of lemon juice. This will taker of the sweetness.
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