Small Battery Pack

Got an in-line instrument pod sitting on an in-line Carrier.
I want to find a tiny lithium battery pack capacity of running a 12v voltmeter and clock?
Must be lightweight compact so I can install near the gauges if possible?
Appreciate your assistance
Lee
I want to find a tiny lithium battery pack capacity of running a 12v voltmeter and clock?
Must be lightweight compact so I can install near the gauges if possible?
Appreciate your assistance
Lee