As mentioned above, there are smaller /\/\ options. I have also used Speco 5 Watt speakers when the need for water resistance was more important (although, the standard Motorola speakers are pretty resistant to spills and moisture in their own right). Note: Speco 5 W speakers could be damaged if the volume is cranked up too much.
I have used the one Ubbe posted above, and they work well with Motorola mobile radios. Know that you can still cut the ends off of the speakers (if they come with an end), and pin these out to other radios. I often use the speaker posted above with Motorola Trbo series mobiles with the larger accessory connector, for louder audio or remote audio out from a mobile mounted in a rack in another room.