I don't know Lotus, but this usually works on Windows:
1. Make sure the NumLock light is lit. Press NumLock if necessary.
2. Press the Alt key and hold it down.
3. Using the numeric keypad on the right of the keyboard, type the number 0150.
4. Release the Alt key. Hey presto! (Hopefully.)
For an em dash, in case you need one, the procedure is the same, except that the number is 0151.