Thanks for the inquiry.
The Mission Small Double Bed 4ft requires a 4ft Semi Double Mattress which measures 120cm x 190cm. We have a couple of Semi Double Mattresses available which price starts at €179.89 or £124.06 with our best seller Zeus Semi Double Mattress - 4ft - http://www.lovefurniture.ie/bedroom/mattresses/sprung-mattresses/zeus-mattress/zeus-semi-double-mattress-4ft
More mattresses can also be found on our General Mattress Section - http://www.lovefurniture.ie/mattresses
We have free delivery all over Ireland and you can order with card, PayPal or cash on delivery. If you require anything further please do not hesitate to contact us.
Love Furniture Team