How to detect lead paint on a bicycle?
Two chemicals are used in lead test kits: sodium sulfide or a rhodizonate salt. Sodium sulfide should be easy to obtain (or synthesize), and is useful for light-colored paint, as it produces a gray or black color change. Potassium rhodizonate can be synthesized from inositol, but you might be better off getting sodium rhodizonate, e.g. from Sigma-Aldrich for ~US$35 for 5 grams.