I'd like to buy 2-3 more.

Or better, the best price/vendor for OEM batteries.

$94   from dronepartsplanet
$100 from drone parts pro
$130 from B&H Photo

They look like OEM batteries.

Any tips appreciated.

thanks

I wouldn't recommend using any 3rd party batteries. If there is any damage as a result of using them, it will void the warranty of the aircraft.

way out of warranty by now.

where is best price on DJI battery?

I bought one of these, works fine https://geek.wish.com/c/58c75e07922ac67128ce2ddd

If the place you purchase your battery is a "certified" DJI dealer you should be good to go. B&H Photo sells genuine DJI products.