If all other buttons except power button on the remote control works, the fault should be of remote control. Its internal circuit will have a break; and is irreparable. If no buttons works, check the remote control for its infrared emission. For more information http://electronicshelponline.blogspot.com/
. If the remote control is found faulty, buy a new one.
If you wish to buy its original remote control, you have to contact the authorized service center. If you wish to buy a universal remote control, you should know about, which brand remote control have setup code to your TV/device brand. You should first make sure about the number of digits in the codes to your device have. There are 3-digit, 4-digit, 5-digit and even 2-digit codes. You can get this detail by the code list attached to every universal remote control. The brand name of the remote control you select isn't a matter; but, its code list should have setup codes to your TV/device brand, otherwise you can't set it up with your device.
Check this link and note which brand remote control have set-up codes to your device brand, and buy that brand remote control, according to availability. For more information http://electrohelponline.blogspot.com/
Setup procedure, and setup code list to many popular remote controls are given. Pull up older posts.