The old fuse will be marked with its rating - often stamped on the metal end cap - a hobby electronics store wil sell you one.
Current in Amps is very important
Voltage rating slightly important
Length (usually in mm) of vital importance
Else it wont fit in the holder
Amazon sell fuses - put in 20 mm fuse - for instance and see what turns up - over 10,000 offerings - but an electronics store is probably best.
You're seeking a fuse of a specific Length & Current - NOT a fuse for a particular device - the fuse doesn't care what it goes in.
Good luck..., February 2015