I bet a Biro (any old pen/pencil) is cheaper than trying to find a tape..... unless you still listen to Black Lace and wear Terry Towelling Socks
I have loads, but no Black Lace or Terry Towelling Socks.
You don't need a tape in there, just use a the non pointy end of a biro to push the mechanism in, it will stay in as long as you don't push the eject button
Less Hassle than a biro.