Welcome to Grace. Have you looked at joining a clinical trial? This is the safest way to take a drug that is not otherwise regulated and there would be no charge. It would be inappropriate for us to recommend a brand of vitamin even if we did know of one. The supplement industry is not regulated in the US so there's no way to know how safe it would be. I would be especially leery of looking for a cheap alternative. That's not to say if it's cheap it's bad but if it's cheap there's a greater chance that it's because the product is inferior. An inferior product could cause more dramatic consequences for someone already sick with cancer. The risks are high, the cost is high and there is little data to suggest that the benefits would outweigh the possible harm.
When looking at data is important to know a bit about how a drug is vetted. This is a good overview. More often than not lab and animal testing that is positive are not when used in human (clinical) trials. There are usually 3 phases of clinical trials and most don't make it to phase 3 because of outcomes in prior phases. All this to say just because something looks promising in the lab or in animals is far from having positive outcomes in human studies. It appears vitamin C isn't harmful except for those with kidney issues but really there isn't enough data to say it's not harmful. A trial is the safest way to try new treatments because the team keeps a very close eye on the patient.
Here is a good explanation of what is known about cancer and vitamin C from cancer.gov
Here is a list of clinical trials studying cancer and vitamin C. There are 6 trials recruiting or going to recruit from clinicaltrials.gov
Good luck moving forward. We need new cheap safe ways to battle cancer and it's symptoms.
To keep advertising posts at bay it is our practice to not allow reference to online sales especially those that have no clinical data pointing to efficacy. So I took your reference down.