Like that new Fusion Reactor Core?  Don't like the 5x5x4 size?  Ya, we don't either.

We got you.

Here is the WAG version.  Not only is it now a 1x1 model, but it's more powerful!

Energy Input: 10  (super cheap to run...you can even power this with solar)
Energy Output: 2M
Size: 1x1
HP: 10K
Radiation: 0
Blast Damage and Radius set to 1.  This means it won't chain react and blow up other stuff in the event you get beat up.