As the Diva uses Pentaconn connection, it's actually extremely elusive right now for aftermarket cable as far as I could tell. The only one I found was from the actual Pentaconn website itself, you can find the 2.5mm balanced cable and 3.5mm SE cable here, but honestly they look abuot as thick as the one that comes with the DIVA so if the issue is softness I dunno how much this will help you... The ones I am linking are their sterling silver cable, if you browse around there's also a silver plated OFC cable, the quality I have no idea because I've never tried before...
https://pentaconnglobal.com/products/NBB1-12-101-12/21 (2.5mm balanced, sterling silver cable)
https://pentaconnglobal.com/products/NBB1-13-101-12/31 (3.5mm SE, sterling silver cable)
Appreciate it. Unfortunate since I really love the Diva but hate this cable.