pinking shears are the scissors you are talking about- they tend to be rather expensive but if taken care of will last a long long time (i as using my grandmother's-who passed away 20 years ago) do a search for pinking shears- my are Ginghers
as for your backing- do a search- under cotton fabrics-then for (wide backs) or wide goods---many on line shops carry fabrics which range from 108" to 118" or even 120" wide- then if you purchase 3 yards you have 108" x 108"+
i do not know what is available in Spain- but some of the shops here in the US does ship overseas-
i buy alot of fabric from (fabric.com) which i believe does ship overseas- and do carry a selection of wide fabrics- if you bring up their website- click on the quilting fabrics link- then the backings link.