My Samsonite Trekking Premium DV80 is just what you're after, I think Ali. It's a shoulder bag which has two parts to it, which you can use together or separately :
The main bag is just big enough to comfortably hold a DSLR with a lens mounted. You just take that part of the bag with you if you won't need to change lenses. This part also has a front zipped pocket (under the front flap) with handy pouches to store sd cards, spare battery, filters, light meter, or other small paraphernalia. The front flap secures via velcro, so it easily opens but doesn't flap about. This part of the bag is a top loader via zip. It has a flat pocket on the rear for slimline paraphernalia, such as notebook, cleaning cloth, expodisk, or other flat accessories. It has belt loops on the rear. The shoulder strap is detachable + it has a short carry handle on the top, so you can carry it by hand.
The 2nd part is detachable + will comfortably hold 3 lenses, or whatever else you choose to carry; it has detachable/movable internal partitions to protect lenses from knocking into each other or falling about. It joins onto the underside of the main bag via velcro + straps/clips. It's a side-loader via zip, so is easily accessible when attached to the main bag.
The shoulder strap is detachable, adjustable + mega-comfortable, well padded on the shoulder.
Measurements :
Top bag HWD = 15 x 25 x 15 cm
Lower bag HWD = 10 x 25 x 15 cm
The bag is versatile, feature-rich, compact, extremely lightweight + is well padded to protect your gear. It doesn't cost a bomb, I think I paid around £25 on Ebay.
I thoroughly recommend this bag
