Hello Katkin,
if you type in (sharp remote control hand set) there are some that are worth looking at. particularly on (amazon) don't forget to check the number on your hand set and then see if there is a replacement one which you most likely can buy on line.
it might also be worth a try popping into your local asda if you live near one , they have a few on show and some i believe are universal, you must have a number on the hand set which will help find a replacement
how ever a number of super markets have a few on show perhaps your local one also might be worth a visit,. even a local electrical shop might also be worth try,
good luck don't give up as I'm sure even searching the net you'll most likely find a replacement.