I have the 65l Berghaus which I am very happy with and I think meets all your requirements (except 15l too big)
The Trailhead 65 Litre Rucksack, from Berghaus, is a large rucksack that offers fantastic value and comfort ideal for a multiday backpacking adventure.
The Trailhead has a BIOFIT™ back system which offers an easy to adjust back length, pre-curved hip belt, adjustable removable chest strap and top tension straps so that you can adjust the fit of this rucksack to best fit you to be able to offer you all day comfort.
This durable and generously sized rucksack has a large main compartment, base compartment with bivi divider, side bottle pockets, top lid pocket and fixed side pockets ideal for organising your all your walking gear. It also features a rain cover for if you get caught in a downpour, walking pole attachments and is hydration system compatible making it an ideal and rugged rucksack for hiking! Capacity: 65 Litre[/font]
Durable Esdura 600D fabric
BIOFIT™ back system
Top tension straps with adjustable take off points
Height adjustable removable chest strap
Pre-curved hip belt
Attachment points on lid
Fixed side pockets
Bottle pockets
Rain cover
Base compartment with bivi divider
Hydration system compatible
Top lid pocket
Walking pole attachments
YKK® zip
[Size: H77 x W44 x D30 cm
Weight: 1.7Kg
Berghaus Trailhead 65 Litre Rucksack