I have a MM 522 pump, and I am not gifted in the "upstairs department" at all. But thanks to Victoria's Secret, and even Walmart padded bras, I can usually place my pump in one padded bra cup, and no one knows it is there. On hot days, I get a little baby sock , slip in the pump, and pin it to the inside of the cup .
I have never been able to wear those pump garters, as I have big thighs and calves and they would fit like a tourniquet. Never had a problem if I use the padding in a bra. I . Some people have said to put a pump inside a Spanx or such a garment when you have on a sundress, strpless number, or a maxi dress...but I haven not tried that...Seems like you would see the "box" outline if the fabric was knit or clingy.
If I am wearing business attire ( Pant suit, or skirt set and jacket, I just clip it to the waist band or the belt loop. Most people do not pay any attention to it at all. I read about a young woman who had devised a little strtech sports purse that has some type of acronym name,( I will have to research it to get the forgotten name), that fits tight to the body, for carrying keys, electronic gear, pumps. I will do some research and post the link.
Do you use the regular pump clip or that "revolve around the world" number? I found the one the that turns around is too bulky and heavy for daily use, and it breaks relatively quickly from nomal use.