I have been pondering the very same question for some time. I've thought the best way would be as Norm says and plastic weld it. You can use a hot air gun or alternatively using a soldering iron but as Norm says I reckon you would need a donor catcher to cut up for filler. There is always the chance one of the plastic welding blokes in the yellow pages might be able to do a nice job but I hear it's quite expensive. It might b worth a look at buntings for a hot air gun but it needs to be variable temp. Have you tried youtube? There is no doubt someone doing a how to on there and you can decide if it's a "how to" or a "how NOT to".
