Looking for something I can chuck in the Camelbak that will keep a light shower out, is breathable and packs up to the size of an orange, for example. I had a Montane Featherlight a few years ago that was great but I lost it at a festival! Tried an Endura Pakajak on earlier which was nice but only windproof. Budget top end £50 as I already have an Endura MT500 jacket for when it’s truly shite out there…any recommendations?

Montane still do the Featherlight…

I’ve a lightweight Altura jacket but can’t remember the model since it’s about six years since I bought it! Packs down to the size of an orange. Looking at their site the most similar current model is probably the Pocket Rocket but it’s £75

Madison do a tiny packing cheap one. About £18-£20 on eBay IIRC.

Not the cheapest on eBay, but choice of size/colours.

Just bought one of these (currently on offer for £30):
BBB Pocketshield

Weighs just under 100 g (medium size), has a stuff bag built into a pocket and a vent in the back. Fits into my saddle bag (medium Topeak Aero) along with usual spares/tools and phone. I haven’t had the chance to use it in anger yet though (in spite of the recent weather in the NE 🌧).