They are essentially much like a 0.1" or 2.54mm pitch Harwin connector, which can be bought from
www.cpc.com
You need the housings (plastic outer), the crimps (metal pins that attach to the wires) and a suitable crimp tool (to attach the crimps to the wires). These are all cheap...except the crimp tools, which if you want good quality ones are hundreds of pounds!!! Those would give you perfect crimps every time, time after time...and are suited to production volumes, the cheaper versions don't offer such good crimp quality, and rely heavily on your hand eye coordination to get the best standard of connection! Practice a lot first would be my advise as it's very easy to get it wrong and they don't come with instructions so a bit of trail and error is inevitable.
Part no's I've used as follows:
HARWIN M20-1060300 - 3 way housings, pack of 10, £4
HARWIN M20-1180042 - Crimps, pack of 100, £9...you'll use a lot of these practicing!
TL01733 - Cheap crimp tool, £20 approx
The only difference I've been able to spot with the housings is they don't have the polarising features that they have on some servo's etc.
Total cost is pretty high even with the cheap tool, but it will mean you can fix any servo/receiver type connectors...if your game for a bit of practice at getting it right!
This may not be the only solution...but it's worked ok for me up to now, hope it helps.