Looking on eBay at these padded inserts but can't really see what you mean? Can you link me a few?
Here's the exact one that fits perfectly in the Lowe Allpine Centro
http://www.ebay.co.uk/itm/DSLR-Fold..._Camera_Cases_Bags_Covers&hash=item4aaf25c0b2
I've actually bought this one which is where all the gear goes, it has a closable padded main flap and also 2 internal small flaps which are perfect for closing over the top of my DSLR for additional protection.
I've also bought an additional slightly larger insert, stripped out all the partitions and dropped this one into it for double protection and it keeps it's shape much better when outdoor gear is placed on top. Here's the side view of the bag, not the best shot but hopefully you get the idea.
You can see the backpack also has an excellent large internal pocket where I store all the "bits and bobs". Currently in the insert I have:
Pentax K5 body with 17-70 lens attached
Lee small filter case holding 6 lee filter
Lee foundation kit with 2 adaptor rings
105mm polariser in a plastic protective case
rocket blower
12-24mm lens + 35mm prime
2 spare DSLR batteries
small metal case for SD cards
Hoya 67mm polariser in plastic case
12-24 lens hood
The strapping on the front is also near perfect for carrying around my Benro CF tripod, keeping it central for best balance when scrambling etc.
I've bought, tried and quickly sold the Clik Elite Contrejour 40, Vanguard Skyborne 51 - expensive bags but just not good enough for the money, or infact any money!!
I also had a quick look at the F Stop Loki, owned by Joe Cornish as it happens, and whilst I'm pretty sure it's the best designed photo backpack you'll get it's harness system and access to the equipment are flawed IMHO.
I'm amazed that one of the hiking backpack manufacturers hasn't seen the opportunities for this but in the meantime I think I've found a solution that's as good as it gets at the moment for me, total cost was around £120 for the backpack + 2 inserts