I had a 4/4 with the same problem. Got fed up with forgetting to cancel my indicators because I couldn't hear them. I overcame this by simply clipping a guitar pick up (couple of quid from Ebay)to the fuse/relay box. The connecting wire feeds through the existing driver's side bulkhead wiring grommet and connects to a mini pre-amp unit (£12 off Ebay). With some modification to the unit this can then be discreetly tucked away between the driver's seat and the car interior. I have put mine in a small pouch. It works a treat! It is powered by a 9v battery, so no need to mess about with the car's wiring and the volume and tone (if you so desire) can be adjusted accordingly. Make sure that the pickup is as close as possible to, and preferably just touching the relay and you will only hear the indicators clicking. If too far away you may hear a little auxiliary engine noise.
