I would recommend doing a search online through the search engine you usually use. It should show a number of places that sell them. They are not cheap though. Spending that much, mainly for the Red Matter Capacitor is a lot. The Plasmonic Leech can be purchased with just a little EC farming, and can stack up to 10 times.
That is what I use on a few of my characters. You can get up to +10 to all subsystems. With the right skill build, DOFF, and BOFF setup, you can run 125 power to 3-4 subsystems at least every 2 mins without the RMC.
I have bought 2 copies of the CE from ebay for less than ?10 each (one for me, one for my wife) so they are out there (I even managed to get hold of a new Walmart one from Canada for same price but that's not really worth the skill points boost and the boost can't be used on anything but Fed characters).
One trick to be careful of is to make sure the codes have not been used and you are buying a brand new copy.
I've seen them on Amazon and ebay regularly, sometimes on play.com but not many other places.
Of course, this is all UK so may be different where you are but don't give up hope.