So I found these new batteries which I think would probably be one of the better/cheaper options for portablizing.

I don't know if anyone has found these/posted them yet, but they are D sized NiMH batteries with 10000 mAh, and weighing only 160g each. They are rechargeable and they only cost around $6 each. After buying 2 holding pieces for $3 each, you spend a total of $18 for the batteries and holding piece, and $20 for the charger. Thats a total of $38 for 20000 mAh on rechargeable D sized batteries that can be more easily replaced than opening up the entire system to remove the battery pack. And this option looks like its a lot cheaper than every RC battery I have seen (even the batteries that have only 8000 mAh that cost $75 each.)

Remember that I am not including shipping fees

If there are better batteries than these ones, let me know, if not I'm just putting this out there, because I assume someone will probably make a better looking post about it.

Any other technical information I don't really have atm, but you can find the products here:
Energizer Family Charger CHFC Battery charger - 4xAA/AAA/C/D, 2x9V
Premium Tenergy D Size 10000mAh High Capacity High Rate NiMH Rechargeable Batteries
D Cell Battery Holder