I used constantan wire otherwise known as copper nickel 56/44 or eurica wire. I used the same diameter as the original. I think the resistor shown in the picture was 12 ohms and used 0.8mm wire. It is available in small amounts from.
https://www.wires.co.uk/acatalog/constantan.htmlThis is the wire I used:-
125g 0.8mm Copper Nickel Wire
Ref: CN0800-125
Price: £11.05 Exc VAT (£13.26 Inc 20% VAT)
125 gram reel of 0.80mm 21 SWG Bare Copper Nickel Wire (Copper Nickel = Constantan = Eureka)
Data: approx: 0.975 ohms per metre, 125g = approx 28 metres
This is enough to do 2 resistors.
They also sell:-
OXIDIZED CONSTANTAN / copper/nickel
THE OXIDIZED SURFACE IS NON CONDUCTIVE
56/44 copper/nickel
This might be a better choice they didnt sell this when I rewound my resistor about 12 years ago.
Mick