Dave,
Makes me want to abuse my BH account. :/
It doesn't have to be the Burton but anything with a waist strap to put the weight on your hips also. The Burton is very well made, I am a fan of Oakley and it is as well made as those. I have the 26L and if you visit your daughter there is a store there or in Berkeley. I doubt the 500 will fit but a body or two with 3 lenses and other travel equipment plus a tripod will work with them.
https://www.burton.com/us/en/backpac...&sz=24&start=0