Have a good meter? Set it for amps, turn on the flashers, cover one of the wires with an inductive probe, set it to record min/max to get the reading then use R=E/I. The Shack has the resistors. Look at them all then buy a comparatively big, fat one of the right R.

Experience with this varies so I feel compelled to say this: You're on your own if you plan on sticking anything anywhere in the wiring harness of your vehicle.

Please note this is all on an R1200s, but I bet the HP2 uses a similar (probably identical) ZFE module.

I confirmed today that while the rear indicators are disconnected, I get fast blink and lamp error on the dash.

You don't need a current probe to figure out what they draw, use ohm's law for that.

volts x amps = watts

On an R1200S, the rear indicator bulb is a 10 W bulb according to my owner's manual, so it draws just under an amp at 12V.

So according to ohm's law.

Ohms = volts squared / watts

Volts squared = 144, then divided by 10W comes out to 14.4 ohms

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When I put LED blinkers on my R1200S I went down to Radio Shack and bought two big resistors out of the bins o' stuff, they say 20W 8ohm on them. They are about 1/4" square, and about an inch and a half long. I soldered them in series with the LED lamps, so if the lamp opens, the circuit opens and i get a fast blink and lamp error, as opposed to wiring them in parallel and then the lamp could burn out and I would not know.

To quote tm1100s "You're on your own you plan on sticking anything anywhere in the wiring harness of your vehicle"

Good luck.

Actual current draw is 1.2 amps and the voltage can be as high as 14, maybe more. A little trial and error from that starting point but the 8, 10 or 12 ohm 20 watt resistor sounds about right, like Rob said. Who knows what's in the control box but I'd keep the current draw as low as possible to avoid any damage. Simpler would be to find the smallest 10 watt bulb you can find, wire it in and tape it to the inside of the fairing.