tank badges/decals

Just Google "Hen's Teeth" and you'll find some! :-) As far as I know, no-one is making any, other than an odd one off.  I have a Navigator with those badges, but are yours the same?  Their Serial Numbers are on the back.  The Lightweight versions are different to the big twins.  It's possible, but tedious, to restore them. 
First acid dip, or electrolytically treat them to remove all the plating and get back to the base zinc-alloy.  Then you can use metallic epoxy filler, or possibly lead solder, to fill the pitting.  Then you have to finely sculpture and polish the filler to the right shape.  Needle files should help. You should end up with a smooth-finished badge, which can then be electroplated.
I didn't say it was easy! Gateros Plating helped with advice
I bought a pair of used badges just in case they were in a better condition than mine.  It's marginal, but I haven't yet got round to trying to restore them yet! Good luck!

From Norvil m/c. But you might want to sit down before you look at the price. And have a bottle of smelling salts ready.

https://www.norvilmotorcycle.co.uk/pettank.htm

NM227134A BADGE - TANK - SLIMLINE - PAIR - STYLING STRIPS - CHROMED

Norvil's strips are for the big twins - which were originally numbered 22714 for Left Hand, and 22713 for Right Hand.  The Lightweight numbers were 22183 LH and 22182 RH. They are different sizes.  Unfortunately I don't have a parts list for slimline ES2s, but someone who does. will find the badge part numbers.

Don Pender- Triton Motorcycleparts.com list them for Dominators, I brought a set some years ago. tritonmotorcycleparts.comPRE-COMMANDO 

I've been looking fo the same for my lightweight.  I've tried filling, then painting with paint that's supposed to look like chrome plate, didn't work.

I think this style of tank badge would be a prime candidate for 3D printing.  Printed in a chrome plateable plastic (ABS?) they should look indistinguishable from the real thing.

Anyone here with the skills and enthusiasm to have a go?

Back in the 90s, a local sign company who specialised in Plastic goodies said they could make me replica Slimline Badges in Chromed Plastic. As with many such good ideas, there was a catch. Machining the dies and the first set of badges would cost £1,000 but from then on they would be 50p a pair. I proposed the idea to the NOC hierarchy but they did not believe that there would be enough of a demand.
Plan B was to press some original badges into a Plasticine mould and then use a Fibreglass repair kit to produce some replicas. This was fairly successful although sealing the surfaces to take Chrome spray paint did not work very well. Being impatient, I dropped the shiny Chrome idea and opted for a Satin Silver finish which on a bright red tank looked ok.

I have done some 3D printed parts (I do the rear light lenses for the rotary classic amongst other things) there are a number of difficulties.
You need to get a good 3D drawing of the item, even with a 3D scanner this is not an easy job and needs a lot of post processing.
Once printed out, you then need to get the surface perfectly smooth otherwise when 'chromed' all imperfections will show through.
The procedure to chrome plastic is not something that the diy person can really do, it is a specialist job.
There may be members / companies out there with the skills to do all this but it is not something I would attempt.

Has anyone tried chrome vinyl wrap?  Or 'chrome paint' (such as the Revell product which seems to have good reviews)?  Both might be used over a well prepared part (perhaps 3D printed and filled) whether metallic or not.

I have never looked at vinyl wrap but from what I have seen, that is ok for fairly flat or gently curves surfaces. I don't think it would work on the tank badges.

As regards the diy chrome paint, have you seen the price? £23 for 150ml.
It looks like it is targeted at the plastic model making market and is not very robust, so I think that is not a possibility either. Happy to look further into either if people have more knowledge.

I will try talking to a couple of companies based on the concept of me providing a 3D model that they will then print and use vacuum metallising to see if it could be economical or even feasible.

Just a thought. Would it be possible to photograph a pair of good badges and have transfers made that give the impression of badges with the rubbers?

This company seems to do what's needed.  https://www.chromespray.co.uk/

Very little information about durability and none about cost.

If you use electro-conductive paint, you can electroplate almost anything.