I think you answered that yourself earlier:
this is a honda 2 stroke unlike the s90 , there seem to be very few for sale
There's so little demand for them it isn't financially viable to stock them, and maybe for any manufacturer to even continue making them.
Your eventual solution is obvious, simple & the same as most bikes = use a fuse from another source not the battery manufacturer. You economically & sensibly chose to reuse the old fuse, but new inline fuses are readily available, so it wasn't really a problem was it?