We have after a long search - Tanks and seat made specifically to fit your Triumph T140 or any oil in frame triumph (and some BSA's too!)
In fact we tried this on a T150 today and it's a perfect fit! which means it'll fit most unit Twin Triumph frames (oil in or not!)

Goodridge hoses and K&N's.

Exhaust systems in Stainless, high or low level, meggas or silenced.

Mikuni carb kits, tyres 18/19 etc.

The red seat at end with boards fits
tightly over the T140 frame, so is an option if you're good with your hands!
We have just fitted one of these to our T140 - you need to cut it down at the front to miss oil filler and tank/taps, see pics of black seat at bottom! (easily done with hacksaw & file)

Extra pics of Triumphs with Trackmaster Tanks!

On a pre unit Triumph vein, most of our universal seats will go on those cos they have a flat frame base and a small tank end - so our cheaper XR unit or the Knight seat will fit easily (see pics of our T100 Tracker)

Seat unit and pad with orange stripe is our new T140 etc Shorty seat and pad - looks the biz - and fits most unit frames.