Old (1950s) staircase tiles needed - where to get ?

[Steerpike]

Hi all experts,

I need some replacement stair tiles. But being about 60+ years old, they are proving difficult to find.
Anyone know where something like these might be bought?

Bigger:
http://images60.fotki.com/v120/photos/1/2570511/11793953/stair_tiles_zoom_1-vi.jpg

Probably need about 30.