All natural fibre mattress

My elderly mum is intolerant of any man-made fabrics and we're struggling to find a mattress (3 ft firm or extra-firm) that's all natural fibres and doesn't cost a fortune. Gardener Haskins are telling her the Ortho Hypnos one would be fine but its got something called 'e-Olus' in which when I research appears to be made from recycled plastic bottles so won't be suitable. Any suggestions please? Thanks Liz Ashwell