If they were used, it's likely the cleats that came with them are still attached to the original owner's shoes. I spy new cleats at the various online cycle reatailers in the $5-10 range. SPD is a specific style of MTB cleat, and all SPD-MTB cleats are the same. I think Shimano's road cleats are also called 'SPD', but they look very obviously different. Other MTB cleats that look similar will be called something other than 'SPD'.