Saft LS14250 BA - 3.6 Volt 1200mAh 1/2AA Li-SOCI2 Lithium Battery. (Use with the Pet Stop® Universal Trainer remote and receiver.)
Also available in bulk at discount pricing through this link: https://atbatt.com/saft-ls14250-1-2-aa-3-6v-primary-lithium-battery/