You can't find them.
If I remember correctly all soft furnishings have to have a fire safety label.
It's illegal to sell furniture which incorporates fabric without a label.
Either the surface fabric or an underlayer must comply with Fire Regs.
The underlayer does put the nasties a bit further away from you.
Most of these fire retardants will be reduced by washing.
If you can set fire to a bit of the fabric after it's been washed then the fire retardent has probably gone.