Easily available for cheap money (because Harley-Davidson dumped a warehouse worth of surplus units about five years ago), but they're marginally adequate for car/truck usage. The motorcycle headlamp performance standard is very lax, and those Bosch motorcycle lamps are closer to the bottom than to the top of the allowable performance range. They're better than the mountain of Chinese garbage on the market (halos, phony projectors, "HID kits", blue bulbs, "diamond Euro", etc.), but that's not saying much. If you need decent cheap headlamps, you're better off with the H6024NH GE Night Hawk sealed beams.
It's an error to think an H4 headlamp is necessarily a good one. There are lots of poor H4 headlamps on the market. A lot of them "feel" like good headlamps because they throw a whack of light on the road surface right close to the car (or motorcycle), but that foreground light is essentially useless at speeds over 25 mph.