Where do you get these? In game I've never seen them in the mark stores or as rewards or item drops...where do they come from?

mission drops. Or Fleet vaults

but you can always buy them on the exchange, albiet at inflated prices....

They are available by the PvP and Exploration vendors in the High Teirs. But before then you have to get them via drops, rewards, or buy off the exchange.

There are a few quests to yield them as rewards also.

I'd hold off on seeking these out. They are about to undergo some severe changes in how they function and will lose a lot of value rapidly. So right now you'll be over-paying for them.

What Exploration Vendors? Have not seen them on any that I have done business with - from the purple on down...

Which "quests," from what giver, for what level?

In the new world being tested on Tribble, EPS consoles only affect changing power modes (eg 'balaced' to 'attack').
They do nothing in terms of weapon power.
So I wouldn't spend a lot of money on them....

I know the console vendor in the second level shipyard at ESD sells them.

tbh, I use consoles I either get from drops or exchange, But I only use ones better than the ones I have now.

And always buy in advance. A 30K Captain one for less than a Commander one? Buy Buy Buy!!!