Bearmach make +3 inch heavy duty springs for land rovers.
As stated they are the stiffer version they supply, IIRC they only make the softish lift spings in +2 only
Most land rover retailers stock bearmach stuff though most only seem to advertise britpart springs at the moment. Try 'mail order 4x4' for an online price (i can't think of anyone else advertising them at the moment)
Scorpion racing should do +3 springs
Depending on what your are trying to achive with your suspension have you considered +2 springs (there seems to be a much wider range and choice avalible and you already have some) with 1 inch spacers?