18 '' Directional Tyres

[H10TVR]

I know this is a long shot given their rairty but does anyone out therer know where there may be a single Dunlop f1 245/40/18 Directional tyre for my Tuscan ?

I have one tyre that is virtually brand new and don't want to replace both rear tyres if ican possibly aviod it, I would even consider a part (low) worn tyre.