Use the Windows Charmap.exe applet. In the Font combobox select a font that has a lot of glyphs, Arial Unicode MS is a very good choice. Tick the Advanced view checkbox and type “super” in the Search box. The grid will show all superscript glyphs, select and copy from that and paste into your source code.
Or copy/paste one of these: ¹²³⁴⁵⁶⁷⁸⁹⁰
Subscript characters: ₀₁₂₃₄₅₆₇₈₉