If your looking for a hard wired one. https://www.shoupparts.com/WL4800-Universal-Mount-Rotary-Beacon-Lamp-Kit This is not battery powered but is a very nice unit and very bright. Has the rotating mirror around a center bulb NOT the LED type. All you need is a switch. I used this one to add for safety on a zero turn when mowing road ditches. It's quite visible, thinking of adding one to combine as well. 
https://talk.newagtalk.com/forums/thread-view.asp?tid=1114979 | 
Battery powered beacon light for combine transport
