That's the Rosenberger main power cable — the notorious one on the Shimano EP801 Spectral:ON. The part number you've quoted (TPB44EN019OF, Trend/Trendpower harness, Gen2) matches the battery-to-motor harness that's been the single biggest reliability headache on these bikes, so you're not imagining it being hard to source.
The short version: this is a warranty part, not a shelf part. It routes through Shimano's dealer network and is frequently back-ordered.
@Winford flagged exactly this — the Rosenberger connection is a Shimano part that "fails frequently and can be back-ordered," replaceable under warranty. He's not a one-off either: he's been through
four Rosenberger cables over 6,000 miles on his Spectral CF8, and reckons most Canyon EP801 bikes start showing coasting shutdowns
around the 1,000-mile mark.
How to actually get one:
• Go through Canyon warranty first — the bike's under Canyon's cover even though the cable is a Shimano item. That's your fastest legitimate route and it's free.
• If Canyon are slow, any Shimano STEPS service dealer can order the harness against the part number directly from Shimano. Quote them TPB44EN019OF specifically so they don't ship the Gen1 harness by mistake.
• Bike-Discount (Germany) and other large Shimano-STEPS stockists sometimes list the harness — worth a search on the exact part number, as availability comes and goes.
Before you fit it — worth knowing: @Rod B. makes the key point that these SD300/SD50 leads are fragile — pulling a connector without Shimano's TL-EW02 wire tool can internally separate the copper strands, which then causes the exact intermittent power loss you're chasing. If you're doing the swap yourself, get the tool. He also notes the plug connections aren't sealed from moisture, which is why the pins corrode and cutouts recur — so route it carefully and keep the jet-wash well away from the connector once it's in.
One honest caveat: a fresh cable often only buys a few weeks before the shutdowns creep back if the underlying motor/connector is on its way out — that's the pattern in the owner reports, not a knock on your specific bike.
If you can tell me whether the failure is a dead-stop (no power at all) or the classic coasting-downhill cutout, I can help you work out whether the cable's genuinely the culprit or whether it's the connector pin or motor behind it.
