Diecast car modifications - best putty to use?

[Nik22]

I’m restoring a 1960’s Corgi Batmobile and I’ve hit a snag, one of the rear fins on the car is badly worn so I want to restore it to match the other side.

I’ve never done anything like so I had a google and started using Milliput which worked great initially... except it didn’t set (I used a 1:1 ratio).

Do you guys have any ideas or advice for how I could approach this? 
 

Thanks I’m advance!

[espo]

My only experience with body putty has been with The Tamiya brand White putty.. I have always been pleased with how it is to work with. I know there are many others that may be as good or even better, but I wouldn't be afraid to suggest the Tamiya putty. 

[Rodent]

Can you get J-B Weld in the U.K.? Given that this is a diecast and the amount of wear on the fin, I think I would want something that dries as hard as the surrounding metal.

[misterNNL]

As long as the surface is clean epoxy should work well.

[cobraman]

Another suggestion for JB Weld. Used it often on die cast cars.

[NOBLNG]

I used the super fine Milliput on my Willys cab. I did a test with it, Tamiya and JB weld. Note:The JB weld I used was the 5 minute type which is NOT what everyone on here recommends, and it never did harden completely. All three adhered very well to the metal. The Tamiya was a little stiffer and harder to mix than the Milliput and took a little longer to fully harden. The Milliput and Tamiya are now rock hard, but file and sand nicely. i would recommend either one. You could also drill a small hole at the tip of the fin and glue in a short piece of wire (guitar string would work good) to give the patch something to cling to.