Capers! (Quercetin) I knew there was a reason I liked them. Although consuming a large quantity could be pretty intense.
Especially as it looks like pickled capers have only 2/3 the quercetin that fresh ones do. To achieve the 50mg/kg dosage in the study, I'd need to eat 2 kilos of pickled capers... on the other hand, you can buy quercetin in bulk for about 10g/$1 USD, which might be a little easier on the stomach.