A small vial is not a bad thing at that size. They love to tunnel so I like leaving them in vials till they molt a few times and need to be moved. Or use a small deli cup like one of those salsa sour cream to go deals from a resturant. Those work well to.
Sometimes the added depth of a vial can be a blessing. My B. boehmei (1/4" when I got her) LOVED to dash up the side of the vial when I opened it to drop food in. I needed the extra second of travel time to keep her from escaping on more than one occasion.
i keep my tiny vagands sling (about 1/4 inch) in one of those small boxes you buy crickets in. it's about 3x3x1,5 inches and the sling does fine in it. however, mine is a very active specimen and grabs his pinheads right away. so if yours does not take the food dropped before him, you might want to try something smaller.