Recommend me a cycle saddle bag

Some time ago, and without much thought, I bought a frame bag that sits astride the top tube and velcro's around the yoke.  It doesn't fit well, not much room in the pockets either side, and I found out the other day that my phone doesn't fit in the clear plastic pouch that sits abreast the frame.  I can squeeze what I need in it, but it doesn't fail to disappoint.

At Airborne last weekend, we cycled down.  Sally left her bike with me and toddled off for a wander around the display areas that don't interest me.  It started to rain 🙄 Went quickly from too warm for a cycling jacket, to overcast, breezy and wet ☹️

So I've got myself a pac-a-mac type half-zip cagoule type thing.  It's approx. 8"x6"x2":

It won't fit in my current storage.  I don't want to pinch or crush it.  I don't really need to store anything else.  So I reckon a simple (i.e. no multiple pockets, nets or internal compartments) saddle bag should suffice.  Don't want anything large that makes me look like I've got a baboon's ar$e.  Probably 1 to 1.5ltr.  Brooks B17 saddle if it makes any difference, and I'll probably want to move one or two of my rear lights from the seat post to the back of the bag.

I'm having a good ol' rummage on the interwebnet, but given my last purchase was quite underwhelming, I'd be very interested on any recommendations, and equally any avoid at all costs/don't waste your time's.

Ta

Gaz