Wanted - Shoulder Bag

[Merlin]

Folks,
I'm currently looking for a suitable bag for lugging my gear over to RIAT this year (plus other shows).

I have a Tamrac Ultra Pro 13, which is great, but I've discovered that it exceeds the current dimensions for carry-on luggage and there's no way I'm putting it in the hold.

I'm looking at the Tamrac Pro 12 which is smaller and should do the job but wanted to see if anyone has it/used it or can recommend a suitable alternative. It's difficult to get an idea of space from looking at a photo 

Criteria wise, the bag must be able to carry:
 - 2 DSLRs
 - Laptop (15")
 - at least two lenses, one of which will be 500mm

And of course be suitable for use as carry-on luggage.

All suggestions gratefully received 

[Paultojo]

Have one of these spare http://www.7dayshop.com/products/7dayshop-canvas-pro-xxl-backpack-rucksack-DS-020 give me a shout


Paul

[Angry Turnip]

Have one of these spare http://www.7dayshop.com/products/7dayshop-canvas-pro-xxl-backpack-rucksack-DS-020 give me a shout


Paul

That looks like an excellent piece of kit-I have a briefcase hardcase for my gear,but it is a bit cumbersome,and you can`t carry it on your back,just a shoulder strap-I think I will get me one of those.

[Sneaky_Nikon]

Doesn't meet your requirements at all but just in case, I have a genuine Nikon bag that I got on an offer in PC World a few years back and have never used.   Sort of PVC outer, velcro and felt interior will take a single body and a couple of "normal" lenses (you won't get a bigma into it).   Usual filter pockets etc. & it is Nikon badged.   Assuming I can find it you (or another member if you don't want it) are welcome to it. I like my aged Crumplers.

Edit:- found it.   So available if required.