5s will be a bit cheaper I guess?
Looked on Goodyear's website? They might be pulling a Michelin and only selling the common sizes in the UK, i.e. 18" and bigger.
Wonder if you can just buy them without fitting. Not looked at the link btw. Only ask as I've had issues with balancing etc before so I get a lad next door to my work (he works at ats) to fit them.