Where can I find a replacement for Sansui TV remote RC03T?

If you wish to buy its original remote control, contact the authorized service centre, or authorized dealer to your device brand.
To select a proper universal remote control, you should know about the number of digits to its set-up codes. There are 3 digit, 4 digit, 5 digit, 2 digit and even single digit codes, to some brand devices. After confirming this, check the sites linked here. Both the sites have set-up code list and set-up procedure to many popular brand remote controls. Check which brand remote control has set-up code/s to your device brand, and buy that one according to availability? Brand name of the remote control isn't a matter, but it should have set-up codes in its code list, to the device brand you have.
Please note: Every new universal remote control will have set-up code list, and set-up procedure along with its pack. Never accept a remote control, that hasn't both of this. http://electrohelponline.blogspot.com/ Check this link too. http://remotesearch.blogspot.com/ If you see these sites by "MOSAIC" or "Magazine" view, will make surf easier.
Universal remote controls are available at most of the electronic spare part selling shops or online by Ebay or Alibaba.com.