I've lost my centre board / dagger-board for an old (very old) Windsurfer (Regatta) - does anyone know how I can get another - or know anyone who has one in the back of his/her garage somewhere? I found this pic of one . . . Really appreciate any help . . .

In general: try Gumtree, you see about one a year.
Try the loose bits bin at the back of any respectable (?) windsurfing store.
If you're in the Sydney area, try the folks at the DAC, they might have a pointer for you, they sail 1-designs there I believe.

One more option if to buy a full, real old such board for 25$ in Gumtree, you see them sometimes cheap. Gives you spare parts then as well.

Worst case: build your own, it's easy, we used to do it 25 years ago. You probably already know that dimensions need not be precise, if you go that way I'll give you some measurements. An option then would be to build a high-wind one, that is more profiled. As good as the picture shown, but caters for a wider range of winds.

'luck.

(I gave one last year to someone like you - dude was really happy.)

Thanks for the advice from everyone - I'm going try and make one - how hard can it be (famous last words!) - Thanks again, James (currently going sideways on his windsurfer)