replace battery

batteries for Apple devices are not standard interchangeable parts, they are custom assemblies made for a specific model Mac, and are NOT a commodity item.

When available, the best replacement has always been a genuine Apple battery. They are substantially more reliable and long-lived than any other provider.

DO NOT buy batteries off eBay or from no-name vendors.

In the US, Users report acceptable (not excellent) experience with NuPower batteries sourced from OWC at Macsales.com.

That model just rolled off the "supported" list and, as so many were sold over the 4+ years it was in production, Apple may still service batteries if nothing else. You can use this Apple support page to quickly see if they can still replace it with a proper Apple part:

Apple Repair and Repair Status Check - Official Apple Support

If they do, consider the ship-in/mail-in option. I used that option for battery service on an older iPad. I set up the repair online using the above link and then dropped the device at the local UPS store on a Friday morning. UPS already had comms from Apple that I was bringing it, and they even packed it.

By the time I returned home, I had an email from Apple confirming that UPS had acknowledged receipt of the device. Before noon the following Wednesday I had an iPad with a new battery in hand. Six days, and two were weekends. I was impressed.

Aftermarket batteries are never as good as the originals so it's worth investing a few minutes online to see if Apple will still service the battery.

Have had email from mac repair tech he says he has original battery in stock sounds bit dodgy so asked for confirmation ie pics of item before buying.

My understanding is that Apple only suppled batteries to Apple Authorized Service Providers and not "just any" shop with a shingle over the door. I'd check the status of the guy so you don't get stuck with on of those POS aftermarket units. As best they don't work; at worst they could wreck your computer.