I bought some generic 500mg Niacin as an experiment to see if it would lower my cholesterol (instead of taking cholesterol meds - it was 10% too high :P). Most of the Niacin I saw on the shelves was 500mg, & for the cholesterol 'cure' I was taking up to 3000mg a day (after two wks of gradually increasing dosages).

If it helps, according to 2 or 3 different bottles of multi-vitamins, 20mg is the RDV of Niacin, but the only thing I've seen in that dosage is as part of a multi-vitamin.

You might want to contact a store or pharmacy that sells a variety of different vitamins & supplements & see if they have a 20mg variety in stock, or if they can order it - or maybe check out a vitamin website, like GNC?