Oncologist no longer with my Medicare HMO

I haven't posted in quite a while, but still read all your posts.  All was well with me, except for the chronic nerve pain from lymph node surgery until I got a letter from my oncologist in June stating what a privilege and honor it was....blah,blah,blah, however...upshoot he joined Texas Oncology in Houston and they do not take TexanPlus my Medicare HMO. My finances are such that a Medicare HMO was a blessing to me being so much cheaper and by the grace of God the oncologist I selected, (there were only 3 to choose from) turned out to be excellent and saved my life.  I found another oncologist who sounded just as good, got an appointment lined up and my files transferred, but my internist refuses to give me the necessary referral.  I thought I had a good relationship with my internist, have known him for years, and this just floored me.  They have 2 "visiting" oncologists who "visit" to see patients but do not actually have an office there.  I would not be alive today if that was the situation when I underwent chemo, the doctor admitted he was glad he managed to get me through it.  I don't need a doc to squeeze my boobs to check whether there is a lump or not, I do that myself, I need someone who can familiarize him/herself with my history, have an office where records are kept and oncology nurses.  I refused to see the visiting doctor, what to do?  Last thorough tests I had 1 year ago, negative mammogram and short oncology visit and I was supposed to see him again end of Sept.  Now what?  New sign-up time for Medicare will be from mid Oct. and will take effect Jan. 2015.  Hopefully I'll be able to afford a plan with an oncology group close to home.  Ladies, what is your opinion, can I coast along to January or cave in and see the "visiting" doc who won't know me or my lengthy history from Adam?

Thanks for your input, Margeaux