My bank declined to authorise my purchase from this company and as this is the first time my card issuer has declined a payment I'm wondering if they know something I don't. My credit should be very good.
I take it you want a bivvy bag with enough room to get a mat in? Would you be interested in an OR double hooped bivvy bag with a mesh net to keep the bugs out? I've had it years and its just not getting used. The bag also includes two internal straps with Velcro fastening to hold a mat in place. I believe the weight is in the region of a kilo including sack and poles.
And sorry I don't know how to post pictures even if I had a digital camera. I can tell you it cost £200 all those years ago and has been used somewhere between 7 - 10 nights. Oh and its blue in colour if I remember rightly.
Another one to look at is the Osprey Tempest - a woman's fit 20L. When I bought a new daysack I tried on 6. Only 2 were comfy and didn't upset my sense of balance. One was the Osprey Tempest and the other was the Black Diamond Nitro. Although both were comfy I felt the Black Diamond was the most balance neutral with a more positive feel that the weight was going down through my hips and legs.
I'd always suggest trying on for fit. If you do that you'll be surprised how many feel comfortable and how many don't. That said if you can have a look at the Black Diamond Nitro 22L. I actually think for a supposed 22L it might be a little smaller. But it is a close to the back comfy fit which gives me more confidence for scrambling.
As for size I'd say it depends on what time of year you're scrambling and what you'll carry. If you're thinking a full set of waterproofs, maybe a fleece/windcheater drinks flask, snacks ... yeah about 22L should do it. If you are only going scrambling in dry weather you could go for something smaller.