Tank Decal

If they're still available from Triumph you could try Fowlers.

https://www.fowlersparts.co.uk/parts/10651/trident-/decals-british-racing-green

This currently states "Back Order/No Stock" so you may or may not be able to order - worth a phone call to enquire. I've found their web site and phone sales support rather better than WoT and they use the Triumph parts numbers.

I notice that Total Triumph (TAUNTON) are promoting themselves as specialists in early Hinckley bikes, and they have recently acquired a lot of NOS parts, many of which are being listed on the bay of evil, so they are also a possible source.

Good luck. Don't see many Trident 750's so it's definitely worth keeping!

 

Are you respraying the tank then, as they are lacquered over?

 

Why not try a vinyl printing shop?
I’m sure they’ll be able to match up the decals and provide them in any colour you like. They’ll be a damn sight cheaper than Triumph too.