Hariburu

Is there a device(preferrably flash drive size) that has small display that can scan mac address and show it on its screen? I have many DVRs that I need to reset, to reset it, I need to get mac address. I usually plug the dvr to router and use mobile device to see the mac address of the dvr, but I am hoping there is a small device with screen that I can plug in to ethernet port of DVRs to show Mac address on its screen. Does something like this exist? Thank you