<SCRATCHES HEAD> A good aquarium pump that's (over)sized for your reservoir will supersaturate it with enough DO that it'll take a mouse all day to drown in it, lol. Simple and cheap. (If it is a suction-cup model - probably is - consider using aquarium cement or the like to permanently install the thing just to be sure it stays where you put it.)
how about hooking the airstone to an oxygen concentrator that puts out up to 6 liters per minute pure oxygen, i have one i got when i had pneumonia , used it once to super oxygenate a batch of wort/beer and the fermenter more or less turned into a volcano! however it was done in half the time and was some of the best i ever made!