Make up a link lead to a full sized cigarette lighter socket rather than convert everything to the din plug size. If you go to an auto elec specialist they sell the same plug as triumph, you just need to make a small link lead up to connect it to the ready made block connector in the loom ( behind panel ). The whole lot cost me around £10 and took around half an hour to do, that includes making up the lead to convert the size ! Link to expensive american site showing the stuff I`m on about Link Removed
I bought the metric type socket. Actually it's a BMW design, I think, that became a European standard. Then i bought a adapter so I can use American accessories as well.
IMHO the BMW socket is a superior design to the American version in that the BMW locks in place, where the American sort of stays put by friction.
Here's a link to the Company I purchased my sockets. Not sure if they are cheaper else where cuz I respected the fact that this company offered excellent explanatory information and history of the BMW sockets I decided to buy from them. Very fast shipping. Here's the link: Link Removed
The Triumph accessory socket is a powerlet style or sometimes called BMW. I too prefer the connection of that over the US cigarette size. I use a splitter in mine so I have one powerlet and one cigarette so I can plug in my Gerbing gloves and GPS at the same time.