URGENT: what to use to strain yoghurt when you don't have cheesecloth.

I too use a paper towel lined wire strainer. It is convenient and efficient. Easy clean up just throw the towel away.

...clean white cotton t-shirt...

A clean handkerchief is my go-to straining cloth. I have a bunch of super-sized ones that I keep in the drawer with my other kitchen linens. I rinse them out well when done, hang them dry, then pop them in the laundry hamper to wash with my other linens. It's a good idea, whatever you use for straining, to dampen it thoroughly, all the way out to all of the edges. (I suppose this is most important if you plan to save the whey to use for other purposes, such as lacto-fermentation, which I highly recommend!!) ;o)

Try a thick paper towel, like Bounty.

Hummm...reading between the lines here..sounds you expect it to be done in mins...not hours. As most straining of yogurt is long process--overnight even.

Take a normal colander and line with a few layers of paper towels. Let those soak up excess moisture for about 30 mins. Not the ideal solution, but quick for what I think is your application.

A fine mesh wire strainer works well.

Strainer paper for filtered coffee machine is my go-to in emergencies.

Thanks - it's midnight here and no one wants to go out to try to find an open store.

I'm stabbing at the wind here but I'm pretty sure if you have an old pillow case you wanna part with that'll work fine. Just make sure it's clean. It should work the same.