If you have not already, consider getting a referral to a concierge doctor from someone in your network.
https://www.nytimes.com/2017/06/03/business/economy/high-end...
In large cities with rich people there are cash only and concierge doctors who will spend the time needed with you because you pay them for it. The going rate now here in Los Angeles seems to be $1000/hr for an appointment, though they do spend time outside of that on your case of that which they don't charge for.
If money is truly no object, there are services that you pay money who will do research, have connections to top doctors, and ensure the correct diagnosis. The best known one is Private Health Management. There are some smaller firms often started by people who used to work there that are more affordable. Years ago when I talked to some of these my personal case was around $50-100k which I don't have.
Edit: by the way, I don’t think this is an issue that money can solve directly, which is frustrating. If money is truly no object but time is, one option might be to hire a bright college student as a research assistant, as someone else mentioned here.
The US has a healthcare industry, its main purpose is to maximize profit. This leads to a very dangerous distortion of priorities which distortion is institutionalized. Doctors and everyone else have to work within these limitations which puts any patient at a serious disadvantage.
I was speaking from experience — a friend, EU expat in the US hat to return to his European country to get adequate treatment. But in his case money was a major obstacle in the US.
I wish you best outcome and a quick recovery.
Also consider directly funding researchers, research projects, and trials. Research is money constrained — you can fund work that otherwise would not get done.
If however you're in England and the issue is in getting hold of something like Avastin: if money is no object you can go private and get it. Make sure you read the CQC review of the provider, and check the professional registrations of the doctors and nurses.
Capitalism doesn't work for everything!