Can I just get this cable from BestBuy?

It's the one that goes from the eManage Ultimate to the laptop for tuning, or do I need to get this through GReddy?

 

Standard USB A-B cable. If you have a USB scanner, printer, or most other USB devices you most likely have one of these at your house.

Try to get it from a small shop, they generally don't mark up accessories quite as much as (the now defunct) CompUSA or Best Buy; I used to work for Comp, and a friend for Best Buy, and the cables they sell for $30 or $40 we could buy at cost for ~$2.50 or so.