is there an external backup for MAC?

Most any external USB storage device will work with Time Machine, as mentioned.

If you’re working with several Macs or with Mac portables, you can use Network Attached Storage (NAS) with Time Machine support, such as Synology NAS servers, as a Wi-Fi connection to one of those means you don’t have to remember to cable to the backup storage; backups will run while you’re within range.

For directly-attached hard disks, I tend to look for 4 to 6 TB hard disks, as they’re about as big and as cheap as is reasonably available right now, which gets you some depth of backups. Bigger hard disks start to get a little more pricy, and smaller are closer to “why bother” for the small savings over the 4 to 6 TB range…

Any external drive will work.

Back up your Mac with Time Machine - Apple Support