There's no similar paper because none use cadmium these days, as it's use is banned. Your lucky it's still OK, more modern Warm Tone papers including Record Rapid and Portriga after the late 1980's have poor keeping properties.
Ian
I would agree in part, that the newer warmtone, in Agfa's case post 1990, those emulsions do go bad much sooner than the 1980's version.
Pre 1990 Portriga does have cadmium along with a chloride based emulsion are likely the reasons for enhanced keeping properties.
I, along with Climbabout purchased two freezers full of pre 1984 Portriga which still yields wonderful results. It's possbile to roughly date the emulsion version based on the design and color of the label.
I have some old (1970's) Portriga #0 which changed to PRW #1 in the next version of the emulsion, the older # 0 has noticeably superior low value contrast than the later PRW # 1.
Simply stated, there is nothing in today's papers resembling Portriga Rapid, hence, it becomes a choice of what is the best alternative, subjectively speaking my choice would be Ilford's Warmtone albeit a far cry from Portriga.
Cheers