You have at least two approaches here. Start with something cheap and make it work for you. After you get an idea of what you really want go look for it. I'd have to recommend this. You can always let a friend borrow your cheap pack once you get the one you really want.

Or, make the drive now to a reputable outfitter and try on packs that you think meet your needs and have the sales person help fit it properly.

I still use an old Peak (Coleman) external frame pack. I wouldn't say I love it, but it hauls my stuff and still has a lifetime warranty. I've modified it a bit to make it fit me better by adding a chest strap. It was on sale for about $70.00 when I bought it. I've used it quite a bit.

I have a buddy that has two Kelty bags he bought back in 1976. He still uses them. Kelty has replaced a few zippers for him over the years, always at no charge. Hard to beat that.

I also have a Peak daypack and a some Jansport day packs that I use a lot. The Jansport bags were on sale for $14.00 at Target so I bought two. I use one of them almost everyday. I also use them for saddle bags on my miniature donkeys when I bring them out. The Jansport bags are really tough. Again, they all have a lifetime warranty.

Hope this helps!

Bill