Need help receiving care out of state

I have marketplace coverage in VA, as I am self employed. I was recently diagnosed with a rare cancer and my local oncologist wants me to see a specialist in Texas. Of course that provider is out of network for my VA marketplace plan. I spoke with a broker and was told I need a supplemental policy and it will take care of this out of state care. I was told that it would not cover out of state surgery or anesthesia. I was fine with this, as I don’t anticipate needing that. I purchased the PHCS Limited Benefit Plan through US Health. I provided that info to the medical center in Texas. They verified the coverage but told me they would not be able to accept this insurance since it is only supplemental. Two different individuals told me that they only accept full coverage plans. They suggested requesting a “plan upgrade” but stated that is probably not an option with this plan. They also informed me that I could pay out of pocket for the initial new patient appointment and testing, to the tune of about $39k. I have emailed the company about the upgrade and am awaiting a response. If that is not possible I will be cancelling the plan. My question is, does an insurance exist that I can purchase independently that will provide me with “full coverage” for out of state care? Additionally, does what this facility is telling me sound correct? I’ve personally never heard of this.
I’m 37 years old and I’m just trying to live. I’m willing and able to pay for this coverage. I am not able to pay out of pocket (starting with the $39k visit) for the out of state care. Any suggestions would be greatly appreciated.

Edited to add that annual household income is around $250k.