If you're going lithium, this is the best deal I've found. With Cam and BBK usually the extra power is handy to have.
36.99
and something cheaper
I would measure stock battery compared to these and verify Pos post are on the correct size.
I've purchased many batteries through Amazon and you can take your core to an auto parts store and receive a $10.00 store credit in most cases.

Amazon.com: Tusk Lithium Pro Battery TLFP-7L For HONDA Monkey 125 2019-2020
Amazon.com: Tusk Lithium Pro Battery TLFP-7L For HONDA Monkey 125 2019-2020
www.amazon.com
36.99
and something cheaper

Amazon.com: YTX4L-BS - 12 Volt 3 AH, 50 CCA, Rechargeable Maintenance Free SLA AGM Motorcycle Battery : Automotive
Buy YTX4L-BS - 12 Volt 3 AH, 50 CCA, Rechargeable Maintenance Free SLA AGM Motorcycle Battery: Batteries - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
I would measure stock battery compared to these and verify Pos post are on the correct size.
I've purchased many batteries through Amazon and you can take your core to an auto parts store and receive a $10.00 store credit in most cases.