Camlab have a great little testing kit for Lead, Mercury and Cadmium in Potable Water, but it can also be used for testing Lead levels in soil.
The eXact LEADQuick kit is available here at:
This includes the meter itself and enough reagents for 50 tests all included in a handy carry case.
Additional items needed for the Lead soil test are:
Item 1132139 – Measuring Spoon
Item 1129968 – Syringes Plastic Sterile Plastipak Luer Slip 1ml Pack of 100
The method for testing is shown on page 15 of the attached manual.
For more information on this and other water testing kits: