If only a specific button of your remote is not functioning, then the problem might be the contact switch attached to the remote control's PCB. You can have a technician open up the remote to check the specific button and its contact point. These parts can be purchased from DEECO, a local supplier of electronic spare parts. This is usually the problem of remote controls, usual wear and tear over time.
For the RX-V430, the remote control is an RAV-242. A b/new unit is hard to come by these days, though, IIRC.
Should everything else fail, then your next option would be to purchase a universal remote, such as those from Logitech, as what was earlier suggested. Remote controls from logitech are "learning" remotes.
Good luck, bro.