Heavy duty springs for series 3

Hello, I have a series 3 109 ex mod and I was just wondering if anyone knew where I could get some heavy duty springs from? I don't care about it sitting hirer, I just need it to be able to carry more load. I have tried to find ex ambulance springs but have had no luck! Anyone got any ideas?

Could get paras in which case just google them

I found a full HSE kit on google brand new is around £1200, these are 4 leaf paras. I thought leaf springs could carry more the parabolic ?

get 1 ton leafs if you want real carrying