Do you think a rice bran extract would have it?
I don't know, but I found some papers which provide tricin content of various foodstuffs.
This paper says Oryza sativa (Asian rice)
leaves contain tricin at 7,060 mg per kg = 7 mg per gram.
This paper says Oryza sativa
culms (ie, shoots) there is only 0.45 mg per gram.
By my estimates, an oral 70 mg dose of tricin should result in a good antiviral effect against cytomegalovirus. That would equate to 10 grams of the Asian rice plant leaves.
So I was possibly thinking of growing some Asian rice plants in the garden, and harvesting the leaves. I read that these leaves are not normally used for culinary purposes, but are given to animals to eat, so presumably that means they are safe to eat.
The first paper also states that the leaves of Phyllostachys glauca, a bamboo plant, contain tricin at 26,500 mg per kg = 26.5 mg per gram, which is even higher than in the rice plant leaves.