I have a couple or three down here in Oz .
Be aware there are different fitments of different models of Rocket III.
As you have already mentioned the basic difference between single headlight Rocket III Tourings and dual headlight Standards, Classics and Roadsters.
The early 2004-2009 Standards and Classic models fitted with then aftermarket king Jardine's Big Boss complete exhaust header and pipes and the later 2010 on Roadsters have ABS components etc that can also affect mounting systems.
In Australia a now defunct but many decade producer for most motorcycle brands /models was a Queensland based company .
CLASSIC INDUSTRIES :: MOTORCYCLE TRAILER HITCH AND TOWBAR :: SHOP
Online Shop for motorcycle trailer hitch or towbars for Aprilia BMW Bowell Cagiva Can-Am Ducati Harley Davidson Honda Hyosung Kawasaki Moto Guzzi Suzuki Triumph Yamaha Vespa Victory Royal Enfield Piaggio Indian
www.classicind.com.au
New prices below, now the business is shut already.
They did sell a lot of these towbars in the USA too. Australian Dollar prices at the time.
8 'TT17' Triumph Rocket III 2003 to 2009 $475.00
12 'TT21' Triumph Rocket III Touring 2008 onward With hard pannier bags $475.00
15 'TT24' Triumph Rocket III
with Jardine exhausts and Roadster 2010 onwards $475.00
The versions below ARE NOT the R3T 'TT21' ones so you can ID and NOT buy by mistake.
These are all solid bar/plate and not tubed steel.
Pretty sure these below are TT17 Triumph Rocket III 2003 to 2009.
TT24
Triumph
Rocket III with Jardine exhaust pipes and the Roadster. Current model from 2010
Note differences
The one below was Mittzy's Roadster one he sold a while ago. Note the different plate shape at end and much lower rail height to accommodate ABS parts or lower mufflers like Jardines need too!
Drawing/details of extra tab and side struts kindly provided by @Mitzzy
TT24 Triumph Rocket III with Jardine exhausts and Roadster 2010 onwards :