I am a kayak angler as well as a SIB user and we have a whole array of waterproof clothing available for the sport. You are looking at surface drysuits from £299-600 but I use for most of the year a pair of Kokatat high waist paddle pants which are light and easy to take off for a pee.
Kokatat Hydrus 3L Tempest Pant | Escape Watersports
A cag top which has seals on neck and sleeves
Palm Velocity cag 2013 | Escape Watersports
The good thing with these types of gear is they are very light and stop the wind and rain but don't restrict your movement. For cold weather I simply add a micro fleece two piece under suit with tracky bottoms and a t-shirt and fish in dec / jan conditions so I know they work. Should the worse happen and you go in the water, you are protected, okay not a full drysuit but nevertheless for the most part you stay dry with perhaps a damp belly where the two garments overlap.
Because these items or similar are light weight and roll up tight, you can store them on board in a bag taking little space when not in use.
Hope that helps