Take the supplemental HMO offered. Between the Medicare / Part B and HMO supplement, everything will be covered. The HMO should cover the co-pays for Part B. It is the best coverage with one policy complimenting the other. Make sure your HMO has a drug plan too. It sounds like you are in good hands with whoever has you to this point. Good luck!
D/H 47 years old, 10/2014, Stage IV M/CRC, nodes 12/15, para-aortic, 5 cm sigmoid resection, positive Virchow. KRAS mut, MSS, Highly Differentiated, Lynch Neg, 5FU/LV and Avastin 1 YR (Oxi for 5 months) NED 05/2015, Zeloda/Bev since 01/2016. 02/2019 recurrence para-nodes, back to 5FU/LV Oxy/Bev, pending genetic results. "...Perseverance is not a long race; it is many short races one after the other."-Walter Elliot