Brian that style of indicator is popular with the cruiser crowd.
I've already been down that road (actually, it was the first one I tried ~ I'm a HD mechanic as well as Suzuki and Yamaha and knew were to start). The biggest problem I've encountered is that the best Housing I've found only came in LED, and with my LED experience, I don't feel they're bright enough to be worth anything in broad daylight (and I don't much ride at night, so I need Bright turn signals that can be seen during the day). The only bright turn signals I've ever seen are OEMs with 1156/1157 type bulbs.
I've also dug through other OEM options and only found a couple that I sorta liked. The HD Vrod and a Royal Enfield, but both of those have minor things that I don't care for.
I really don't want to settle. If I knew the PN, I could Probably get them ordered.... problem is that the only microfiche I've seen is for US market with the big floppy lollypop type signals.