Various Manufacturers Stem Raiser For Traditional 1 Inch (22.2mm Quill) Stems
Note: "Traditional 1 inch" refers to the type of fork that the stem goes into. The actual diameter of your stem should be 22.2mm (7/8") for this model stem riser.
A stem raiser fits into the steering column in place of your present stem, and secures with a wedge bolt in the normal manner. The upper part of the stem raiser sticks out above the steerer, and is bulged out so that you can insert your original stem. The bottom of the original stem winds up a bit above the top of the headset, so you gain several inches of height.
This size fits most older bikes with "1 inch" stems. Actual outside diameter of the riser (and stem) is 7/8" (22.2) mm. Inside diameter of bulged section of riser is the same as the steerer tube: 7/8" (22.2mm).
Note, you may need to install longer brake and/or shift cables.
You'll need a long 6mm allen wrench to tighten the bolt in the stem raiser.