There are new packs out all the time that will probably work just as well. If you have concerns, shop at a reputable camping outfitter or speak with the Scoutmaster for recommedations. One of a backpack's critical parts is the hip belt. A hip belt needs to fit snugly or the pack quickly becomes unbearable to carry. Be sure a pack fits properly before you buy it.
Most packs have several points of attachment for the shoulder straps and the hip belt.
We can help you adjust your pack properly. You should also have 2 pairs of adjustable straps to attach items to the top and bottom of your pack. If your pack has no place to attach straps, you can add lashing patches very inexpensively. You will need to have a large, heavy duty trash bag to use for a pack cover. Usually, we suggest synthetic fill bags instead of down.