External and portable charger for a Macbook Pro 15-inch, 2015 (no USB-C)

I’m doing a search for external portable chargers for my 15-inch, 2015 Macbook Pro, and it’s been a tough time trying to find one that has enough power to charge this laptop. A lot of the external power chargers out there have a connection to a USB-C port, which my laptop doesn’t have.

Would anyone happen to have any suggestions on which external portable charger to get for this laptop?

Any helpful input would be greatly appreciated. Thanks!