Veclan.com can do it. I had them make me a RSA plug to double 3.5mm and it was like $25 and pretty nice (for Pono balanced into a balance headphone amp). I’m sure they can do the 2.5mm vesrsion. I had them make a 2.5mm to RSA adapter as well, so I know that the 2.5mm is a nice tight fit. But you can also just make one if you can solder. I have made the 2.5mm to dual 3.5mm very easily.