@Marniesews, I been thinking of this and you may like to have a look on here to get some ideas of the different fabrics used for an overlay. Net/Tulle, Organza, Chiffon etc.
https://www.harrington-fabric-and-lace.co.uk/plain-fabricLook at the Plain Fabric and the Plain Tulle and Net. Content e.g silk , cotton, polyester, nylon, how they feel (handle) etc.
I presume you are looking for white or ivory, but I could be wrong, however they also show the colour range the fabrics are available in.
They have a large range of fabrics and they give pretty good descriptions.
Prices are on there so if you do find something suitable you can compare prices elsewhere.
Not saying to purchase from there but it will give you something to compare when you look at prices elsewhere.