There's a local electrical shop here where I usually get them. Alarm systems, fire panels etc tend to use the same type as well so any store that deals with either general electrical or maybe alarm/fire panels might have them.
Per watt hour these gel types are bad value though, but when physical space is a concern then it makes sense to use them.
Per watt hour these gel types are bad value though, but when physical space is a concern then it makes sense to use them.