I also have an Armdroid 1 which I'm currently restoring.
The power connector you need is a GX16 (it's a connector used in aviation industry, or HAM radio) 2-pin, 16mm. You can find these easily by searching eBay.
As mentioned, I'm currently restoring my Armdroid - which means I've pretty much stripped it right down and have been rebuilding and replacing broken/damaged parts as I go. I will be documenting my project on a Blog / website a little later this year. In the meantime, if you need any further information, please drop me an email.