I used to smoke Newports and occasionally bought Kools when they were out of Newports.
I like Halo's Menthol Ice. I've only been vaping 2 weeks now, but Menthol Ice (and Tiki Juice which isn't what we're discussing) made it extremely easy.
A 7ml bottle costs $6 or so. Maybe get him a menthol sampler? You get 6 bottles for $25. He'd probably find a menthol he likes in there. If not, you could try them too I suppose.