Holdens supply 52mm (£76+) and 60 mm (£86+) clocks which they say are made from genuine Smiths designs and tooling. What you need to be careful of is the shape of the chrome bezel to match your existing ones.

Doug
2011 Plus 4 in Rich Maroon

1972 750 “ComDom” sprinter
1958 Triton 650
1992 Triumph Trophy 900