@Laurelgs I'm a guy, so not sure how relevant this is but I had the same concern (I'm a bigger guy). I shopped and looked at the measurements for waist and sternum and was a little worried (I've got a 40" waist). I got a Gregory Paragon 58 and the measurements on the specs were spot on. Very comfortable. I also looked at the Osprey Atmos and tried a few on and they were pretty spot on too. Hope this helps.
@Laurelgs thanks so much for your question! Before we can make good recommendations, it would be helpful to know a few things. First, what kind of pack are you interested in? A daypack or one to be used for a short or long backpacking trip? Also, how tall are you? This helps us know if men's/unisex models might work for your torso length. or if we should focus on women's-specific packs only.
If you are interested in a backpacking pack, you might consider a model that has a removable hip belt, which will allow you to swap out hip belts. So, for example, you could purchase a women's Traverse 65 pack in the correct size torso length (XS, SM, MD,), then swap out the hip belt for a size that fits better. This is often a modification best done in our stores (for free at the time of fitting/purchase), so if possible, you might wait until your local REI store reopens. Or, you could consider setting up a free virtual outfitting appointment in the meantime to talk through options!
Let us know if, instead, you are interested in a daypack and we'll provide some suggestions for those!