Is the Nikon D500 DSLR compatible with an external battery?

The Nikon site says its battery only lasts for 200 shots, which would only last about 30 minutes for my mother who I'm thinking of buying this for. She does sports photography so she's constantly taking pictures. My question is if the camera has a connector for an external battery.

I think you mean the D5000 because the D500 doesn't exist. Anyway.
Only 200 shots? That's standard for most point-and-shoot cameras. I just checked the Nikon website and it says the D5000 battery should last for 510 shots.

http://www.nikonusa.com/....TechSpecs

And yes, there are external batteries for it, which are called 'battery grips.' Battery grips can usually hold 2 lithium-ion batteries that correspond with the camera it is for, or 6 AA batteries.

http://www.bhphotovideo.com/...Search=yes

You can consider a battery grip, though you'll only find ones made by third party companies. Unless your mom shoots more often in portrait format than landscape, getting a few spare batteries would be the most cost effective solution: http://www.bhphotovideo.com/...30mAh.html