M1xsp connector and power issues


I am about 1 month from completing new home and have finished all of my whole house audio and video and now almost done with my M1G and peripherals. I have 2 issues:
1. My contractor got someone to 'clean-up' and he threw away the box that had my connector for my M1XSP for my thermostat. Can I order one of these, or can I use any old seriel cable (I have several lying around.)
2. I went ahead and got another power supply/battery charger (ELK P624) and battery and 16.5 volt transformer when I decided to get the water shut-off valve. Can I use this to supply power to my inputs on an input expander (motions and water sensors total 200 mAmp) and for the water shut off ELK WSV, or is there a bettter way to divide up my amperage needs or is there a way to combine my power sources into one with more amps (clearly I know little about electricity)
Thanks for your help (again)