Can you recommend a shoulder bag?

I have been a pro photographer for over 40 years, and the best shoulder type bag for my uses that I have ever had is the one I use now. It's the Tenba DNA 16 Slim Camera Messenger Bag. Mine is black, but they have it in one other color.

Given what you say you need to carry, this would be perfect for you. There are several reasons why this bag excels: 1) it's slim, so it's easier to carry on your side - the closer the weight is to your body, the less stress it puts on your body and it also is less cumbersome to move with it. The deep overall shape, rather than the more spread out shape of other bags means that you have more vertical room to store gear, even though the bag is slim. 2) the bag stands upright on its own, with or without gear in it, and the bottom quarter of the bag is very rugged rubberized water proof material, while the rest of the bag is very high quality water resistant rip stop nylon or something similar. 3) it has a extra strap with which you can make it into a sort of semi-sling bag, in that you can perch the bag up onto your back to keep it from interfering with your leg movement (that's why it can be well used by bike messengers). 4) it's deep dimension would make it very easy to carry your camera with that lens mounted and still leave room for at least 2 more large lenses, with other spaces and pockets for cards, batteries, etc. Here's what I have worked out that I can routinely carry in mine, without the weight and size making me uncomfortable or preventing me from walking with it all day: my R5, an RF 70-200 f/2.8, an RF 24-70 f/2.8, an RF 14-35 f/4.0, and an RF 100-400 f/8.0. 5) The shoulder strap is unusually comfortable and stays in place on your shoulder and the special very tenacious velcro for bag closure has a "silent" open feature that cuts down tremendously on the famous velcro "ripping" sound for those times when you need to work quietly, like during a speech at a symposium.

YMMV, but I really love this bag.