U have 2 options: Wait till new year time, and they themselves will offer a floater card to u (mostly a cobranded card like swiggy). Last yr they offered me Tata neu plus as floater on existing Swiggy card. Or the second option is to cancel ur Tata neu plus card and apply again for a core card first during new year time. U might get Millenia LTF.
2 months back same thing happened with me. I sent an email to grievance team and priority team and they called me and asked me which card I wanted to apply and I can manually apply for that card. They were ready to assist me or they asked me to contact the nearest Hdfc bank branch and apply via the credit card team and approval will be as per their internal policy