[Elecraft] K2 12 volt power jack for amplified speaker?

[nz7c at cox.net]

Hi folks -
I have a Motorola amplified speaker that I am about to wire up. While the K2 is in my shack I would like to have the speaker's voltage supply come from the K2 - ie make an accessory jack. 

Assuming the K2 has the on board battery installed,  where would be the ideal place to tap off the voltage and would it create any problem for the K2? 

That's correct I am not a techy or even a sub-sub-techy :-) Thanks for the help in advance!
73/Tim NZ7C