There are many possible sources of battery power. A flashlight, tape recorder, or other battery-holding piece of equipment may be modifiable to provide power. This has the added benefit of having equipment that does double duty. W6WWW modified a broken electric drill handle to provide an ICOM HT with 9.6 volts from a Makita rechargable battery, while I to get power from a modified Maglite. There is also the time honored method of building from scratch.
Battery holders comes in different shapes and sizes.
An eight cell AA holder makes a very compact 12 volt supply using alkalines, a ten cell AA holder is available for making 12 volts with Nickel based batteries. Consider how to power each item of equipment based upon how you will likely be operating. A Shadow has different needs than a Mobile OR Portable station. Also consider the battery needs for personal pagers, test equipment, hearing aids, etc. Consider the range of power each piece of equipment will tolerate.