Sure, you can get both creams topically OTC.
Niacin is a cutaneous vasodilator, and most cyclists know what embrocation/capsaicin creams do.
Not a bad idea to market … maybe hit up mad alchemy (www.madalchemy.com) since they make some awesome and HOT embrocation that most cold weather cyclocross racers know and just add in some topical niacin cream. Maybe call it, Flaming Fingers or something? 