I have a Manfrotto Off Road 30L with a purpose fit (comes with the bag) padded insert which is side access. It's pretty comfortable to wear, plenty of room for clothes, food, drink, tripod carry, etc I sometimes found the side access a pain especially shooting primes & swapping lenses - that may not be an issue for you.
I also have an Osprey Kamber 42 which is rear access & fits a Pacsafe padded ICU.