On page 5 of the Parallax PDF it tells the values of the diodes and the capacitors. It calls them C3 and C4;
"Component selection for the HIP4081A is relatively simple. I selected the Harris
HRF3205 MOSFET which has an Rdson of about eight milli-ohms (0.008 ohms) for the
four H-bridge switches. The charge-pump diodes selected were from Digi-Key, but
virtually any 60V Schottky diode would work for this application. The charge-pump
capacitor (C3,C4) should be at least 10 times the input capacitance of your MOSFET.
The HRF3205 has an input capacitance of 4000pF. I used 0.22uF capacitors, which are
oversized but worked fine."