Go to the pioneer website and buy the remote for your model from them directly (They usually carry a good stock). You might also be able to buy a pioneer remote off of ebay. Most pioneer remotes will have the loudness button, but you might want to double check with pioneer if certain model remotes can work with certain receivers.
Also, a lot of newer remotes are programmable and can probably be programmed to work with your system. Good luck.
I have an older VSX9500s, and there is or never was a loudness control on the remote, nor on the receiver. The only way to turn the loudness on was by thumbing through preset bass & treble settings, and one of them made the loudness turn on.
Of course, yours is a different model, but I just wanted to let you know that a new remote might not help. If yours is an older model, you might not want the remote anyway. Those older remotes were junk compared to those of today.
I have actually tried a few universal remotes...they won't make the LOUNDNESS turn on, but it can adjust my DSP settings. I was wondering if those HARMONY remotes will work or any other type. The ones from Pioneers are too expensive. Thanks!