Simple Rx pack will do. I've been using them for a long time now and trouble free. I would use a lipo Rx pack if your electronics can handle and needs that much power to work at its full potential. I would still go for a good nixx Rx pack.
One of what, a nimh or lipo rx pack? Anywhere that sells batteries will have rx packs- try hobbycity or amain etc. The rx packs are the small sub-2500mah packs generally that come with rx or mini connectors rather than a deans or trx plug.