Just a thought, if 2A is for "Radio Memory" on some models it might have constant power and not be controlled by the key switch. Just something else to consider when looking for a power source, do you want "always on" or "switched" (controlled by key switch)?

 

You just need a couple parts.
Look at the link from installing heated grips. Figure 6, you need something similar, your parts guy may be able to order some. Like Charlie said the picture you posted ECM, Battery and Radio Memory are hot 24 - 7.

http://www.harley-davidson.com/app-c...ts/-J04259.PDF

 

Sure would be easy to just fuse it as close to the battery positive post as you can. The relay gives you a way to turn it off.