Not sure what do you meant by increase authentic.
Increase the chances getting authentic porter from 2nd hand seller ? If the product's price too good to be true. You got to be careful and examine it before close the deal.
However, the best way to get Yoshida porter product/Head porter is purchase thru online since Singapore don't have physical shop for that.
I have been surrender last week, they did not bring in porter product anymore.
Official Headporter
store.headporter.co.jp/en/
or
Provide authentic porter product (HongKong based)
head-porter.org