076 is a good suggestion, but finding them's another matter. Member Steve Gonzales loaded 076 horns on 2404 motors with apparent success recently.
2405 is not far off from what you're wanting, actually:
Dispersion (6 dB down points, 1/3-octave band, pink noise):
140° horizontal x 40° vertical at 10 kHz
90° horizontal x 35° vertical at I6 kHz
65° horizontal x 30° vertical at 20 kHz
If that's too "beamy" for your preference, I'd just go directly to 2404.
OR look at what JBL does for UHF in some of their 60 x 40 controlled directivity offerings, if anything....