Lightspeed attenuator lithium battery pack

I'm going to pick up a lightspeed attenuator but am not certain which 12vdc lithium battery packs on e-bay have 2.5 mm, center positive, plugs. They aren't listed anywhere and I can't figure out how to contact the sellers to ask them. Can you guys help me with this? I'd like to keep it as inexpensive as possible ($20?) and I do want battery vs. wal wart.

Also, what do you think is going to be the best 3 foot rca's under $50? I am thinking signal cable analogue 2's because they have a low capacitance and are $50 a pair. What do you guys think?

Thanks!