Hi there
You could try
http://www.pondsafety.com/ - they will come and fit the safety system for you. They certainly make the pond safe, but you can see them through the water, and they need to be pressure washed atleast once a year... not the most pleasant of jobs!
Aside from that, why not get rid of the pond - add some drainage holes in the bricks at the sides and fill the pond to make a new planting bed, or (if its a strong wall) fit a trampoline and safety rail in the centre - you can plant around this with child friendly plants to make it look more like a pond and soften the edges. If you would still like some water in the garden there are loads of child friendly options, like steel balls with water cascading over the edge - perfect for small hands and there is no depth of water exposed as the reserve tank is concealed.
Good luck! If you would like me to come and take a look let me know - I am a Garden Designer -
http://www.rosienottage.com or 07967 316259
All the best,
Rosie