A range of nylon classical, or Spanish, guitar strings for sale by Augustine, D'Addario and Martin.
It is important to change these quite often, as after around 4 months the tension in the nylon will degrade, giving you tuning problems.
Classical guitar strings come in a few different gauges, known as the 'tension'. If in any doubt, go for regular, or normal tension. Hard, or high, tension strings are, well, higher tension, so will be a little more difficult for beginner players, but have a somewhat sharper sound. Excellent for recording.