Try the Phonak Naida L30 SP it uses size 13 battery, and is a bit smaler than Naida L30 UP which uses bigger size 675 battery.
Phonak have universal bluetooth and connect seamles with every available bluetooth devices, whereas Oticon , Signa, Widex , ReSound and others are only connecting to certain High-end Android smartphones, and Linux via ASHA,
or via MFI on Apple iphone/iPad/ and newer Apple Mcbooks.