I know this is an old thread but someone else may be looking for this information. I'm another old man on a bike with a 2015 R3T like the original poster. And, being old, I somehow lost one of my keys and I know it's here because I hadn't left my house when I realized it was missing. Anyway, I want another spare key and I found this thread. I checked out the ILCO X270 TCM1 key that worked for Bedifferent but, if the pictures are correct, that key wouldn't work form my 2015 R3T. Not only is the head shape complete different but the end profile of the key is also completely different. I'd be careful about ordering that key if you need one. However, at the same site where I checked out the above key, they do have one that looks like it would work. The head is the same shape and the end profile looks the same as my R3T key. It's listed as a Triumph TMC3 blank. Here's a link:
Truimph TMC3 Key Blank [TMC-3] - $5.50 : Motorcycle Key Blanks, Honda, Ducati, Kawasaki Motorcycle Key Blanks, Scooter, ATV Keys Yamaha, Keys4UrRide.com
Assuming the Triumph TMC3 key is correct, the link also lists equivalent blanks as:
ILCO KAW33
EZ X278
JET TMC3
They (at the link) can cut the key for you if you have the cut code. I ordered one so I'll post back when I receive it in a week or so and let the thread know if it works.