Hi BlueStreak,
AFAIK there is no backrest that has been designed ( yet

)
that can be added to any of the variations of seat that Triumph supply for the Trophy.
In case you haven't spotted it yet - there is a very useful "SEARCH" button on the forum -
always worth giving that a go first - if you type "backrest" into the Search field, and and then click Search,
you will ( as at now ) get a total of 35 different Threads discussing the same thing that you can read up on,
and may find some useful information in one or more of them

Cheers

