The Hubba Hubba Hiney is a great pack that you can wear either on a speed belt as a belt pack or use the straps to carry as a shoulder bag. Offers versatility and ability to pack multiple lenses or even a small camera body.
I love bringing this to assignments when I want to have two flashes and a different lens option easily accessible but don't plan to need. Or on assignments when I've done a poor job planning and want to toss in more than what will fit in the Speed Changer. Shop on Think Tank Photo
(and choose a free gift with purchase when you use my link)