Combine water and flaxseeds in a small bowl. Refrigerate until mixture thickens and has an egg-like consistency, 15 to 30 minutes. Stir in almond milk, banana, grated courgette and vanilla extract.
Mix flour, cocoa powder, sweetener, baking powder, bicarbonate of soda, cinnamon and sea salt together in a bowl. Pour in flax mixture; stir until pancake batter is just combined.
Heat a large non-stick pan or griddle over medium heat and spray with cooking spray. Drop a ladle of batter onto the pan and cook until bubbles form and bottoms are golden brown, about 5 minutes. Flip and cook until browned on the other side, 4 to 6 minutes. Transfer to a baking rack to cool. Repeat with remaining pancake batter.