A deck-mounted compass is an excellent navigational tool for sea kayakers. Brunton's model 70P is designed to go into the deck recess on most British sea kayaks, including those from Valley and Nigel Dennis Kayaks. The low-profile design protects it during rescues, and the card (dial to you landlubbers) is big enough to be seen easily from a distance.
For night viewing, attaching a light stick near the compass is the simplest option.