Some people say they have had good results with L carnosine, pyridoxine (vitamin B6), P5P (pyridoxal-5prime-phosphate, activated B6), magnesium, dimethyglycine (DMG), trimethylglycine, N-acetyl cysteine (precursor of glutathione), selenium, buffered vitamin C, probiotics, pancreatic enzymes. and zinc.
These are non-prescription supplements, and other items. They are no longer considered off-the-wall things. Try each separately on your own. There is some hard science behind each possiblity, but remember, each organism's biochemistry is somewhat different.
I have a friend who has tried five or more grams of L-arginine with one gram of L-citrulline, with excellent results. Almost unbelievable.
Be careful, and be prudent. Good luck.
Online, reasonably priced suppliers are iherb, and vitacost. I am in no way associated with either company.
Personally I have good results with the caffeine in iced green tea, or diet coke, but I have to be careful to cut it off at the right point, and not too late in the day, not much later than noon, or early afternoon.