acerola cherry and milk thistle seed both contain quercetin... milk thistle seeds also contain betaine; note this is from whole seed not an extract.
grind the whole seed into a powder.
I think that these two things would do close to what you may get from the product for much less... you could choose another whole food product for the C like citrus peels.
I dry and grind them all too... superfood big time, quercitin, rutin, C, pectin, enzymes, etc.
BTW - for the quercetin, rutin, etc. just be sure to eat the skins on your fruits and vegetables.