When I sold my C5, I have to sell my USB battery box as well, since that one was also the controller of the motorized focuser. My TG-SP II is using a DIY USB power cable to run, and thus I made another one today.
First of all, I will need a small plastic box. I looked around my home and found that little box for dental flossers should be a good fit, so I pour all the contents into another box.
By fitting a USB back panel socket and a 4AA battery holders inside, it seems to be a perfect fit, so I drilled two small holes to fix that USB back panel socket there. Those small holes could be made by using heated screw driver, very simple and elegant. The rectangular slot should be made using cutter carefully, it's not hard either.
I placed that socket on the side since it's the only feasible location. Originally I wanted to put it on the top but then the battery box won't fit afterward.
Last time, I simply connect the wires with the original shielded thick cable, but this time due to the crowdy small box, I removed that shielding. The red and black are for power, and the green and white are for data and thus they will not be use in this case.
Again, check with a multimeter to make sure everything is correct and expected. Don't risk since some of your equipment might break if connected wrongly.
Finally, solder the cable correctly, and check the polarity again.
It's a very tight fit, originally I didn't check the fitting with batteries but this battery box would become a little bit bigger with battery inside. Luckily, it can still be closed with a little bit force, no need to put foam for this box.
I checked polarity again and then I plugged in my TG-SP II, and it works fine! I guess that I ain't going to extend this one to control focusing motor because I have no more SPDT switch and I have no more mono socket on hand.
This simple project costs $5 HKD (the battery holder) only.