"Jackhammer" grips/throttle
I also don't like the "kit" throttle and grips, with their mostly-plastic construction, and "bicycle" look. When I see an otherwise nice MB build, but I see that familiar set of grips with the yellow kill switch, it knocks the bike down a notch for me. (The most egregious example of this that I've found is seen on the otherwise spectacular MBs built by Derringer Cycles: derringercycles.com.)
For my latest 4-stroke build, with a 2012 Giant "Simple Single" cruiser, I bought a set of real motorcycle grips. They're 7/8" "Jackhammer" style. These are a reproduction of a style that was stock on 1960s-era Triumphs and BSAs. Nowadays, they're popular for custom motorcycles (choppers, bobbers, cafe racers, etc). Mine are made by a Taiwanese company called EMGO, and they're quite rugged, and have just the vintage look I was searching for. Just Google around, and you'll see that these are widely available online. Just be sure to buy a set that's sized for 7/8" handlebars; a lot of 1" sets are marketed for Harleys and fat custom bars. I paid about $20, and I used the kit cable.
For a kill switch, I bought a rocker-type switch from Sick Bike Parts. Also in view in my attached pics are a real motorcycle, cruiser-style mirror; and a motorcycle brake lever (motorcycle-superstore.com).
Good luck.