40mm strap on 38 mm watch

I own a 38mm Series 3 watch.

I want to be able to vary the straps I can use but have discovered that the Apple store offers no straps for the 38mm face other than original or a silver bracelet costing nearly €400!

I don't want to spend €400 nor is silver my preferred colour. Have I any options other than purchasing a non Apple strap?

Could I use a 40mm strap on a 38mm watch, for instance or am I just unfortunate in buying a model not catered for?