Enter the 3-Season Gardening Trouser from Genus (http://www.genus.gs/women/3-season-gardening-trouser.html). I have been using these trousers for about a month and they seem to tick most of the right boxes.
I am always losing my secateurs so a long pocket on the side of each leg means I can chose where to put them. I can also fit my favourite thin Mira trowel (https://www.implementations.co.uk/shop/mira-trowel/) in the other pocket. This is far better than one of those gardening tool belt affairs which I have always thought must get in the way most of the time. I just have to remember to put the secateurs and trowel back in the side pockets once I've used them and not leave them lying around!
Many thanks to Genus for the loan of the 3-Season Gardening Trouser for this review - http://www.genus.gs