In case this is useful:

If you have a chopstick, you can tape the new string to the back and push the chopstick through the hole to guide the string. Other solid objects like a wire coat hook can work, but you have to make sure the tip won't snag.

Hate it when they sew the drawstring / elastic at the back so it's hard to replace (yeah, it doesn't come out in the wash, don't care). Bonus bastard points for that sewing being structural.

There's also something called a bodkin which has a loop to put the new string in and it's like a long needle with a rounded end that gives you some rigidity to push through

Opt for a stretchy, elastic string. Your future self, racing to make it to the bathroom will thank you.

I tape the drawstring to the end of a wire hanger and pull / bend it through the holes.

oh man its been awhile since I saw a post that was on my level.

I recommend that you carefully melt the ends of your cord with a lighter so it doesn't fray and unfurl over time. You wouldn't want your hard work to undo itself!

That's an awfully bright color.

Just a heads up you tied your bow wrong. What you're looking for is a double slipped square knot. It's the same one everyone should use to tie their shoes and it will hold without being double knotted.

How the hell do you fish out the draw string when it gets stuck inside the elastic? I had a pair that somehow did that and now I can’t get it back out.