The paper deals with a special type of inventory model with a one-shot supply and with a random demand in a certain period. In the paper, formulas for determination of the optimal one-shot supply are derived in the case both continuous and discrete random demand. This optimal supply ensures the minimal expected loss from excess or shortage of the goods at the end of the mentioned period. This optimization problem can be solved by means of analytical or simulation procedure. In the paper, both these procedures are described and illustrated by a simple concrete example. The simulation is carried out in Excel.