Eiretyres stock them and will deliver them to whatever fitter you want. I've ordered from them in the past with no problems, and they were quite a bit cheaper than the local supplier.
Give Dave in Dave McCann Tyres a call. Have used him recently for tyres and other bits and he was cheaper than Eiretyres, and that included fitting and balancing.
* no affiliation - just a very happy customer
Why are you only limiting yourself to Yoko's? What car are the tyres for?