Try Dunelm -Mill or Homebase .Ikea, John Lewis, Ebay .

Just try google I am sure you will find something.

Tesco was selling pink and red ones and am sure I saw ones in Asda. Amazon is also worth a go.

red isn't the in colour this year, its all purples and bright greens, i bought my round red ones on ebay last year and as it happens i need more red cushions for a birthday present so looking on ebay later on, ive tried the usual shops but no luck..

Or you could cover your own - really easy with a bit of foam and some nice material.

I bought some red ones from either amazon or eBay awhile back