Make your own substitute:

Get a lot of Sunglo unflavoured yohurt or buy thairu from Indian shop or make your own thick one from milk powder.
Other commercial brands seem to have thickeners and too watery.

Stir in teaspoon of salt. Pour into double layer of some thin cloth in a bowl. (Guess what "cheesecloth" is for?!?!) Tie and hang up, better if kept cool in fridge with bowl to catch liquid.

After most of liquid is drained out, cut into small pieces. You may have to experiment/check to see how firm you want it.

Don't leave in warm air many days so as to avoid moulding.

Have fun.

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