Steel chainrings for 3x9 speed setups I have Shimano M542 with 3 chainrings (44-32-22) for 9 speed chain.

Is it possible to fit it with chainrings made of steel for better durability? I do not mind extra weight. The dimensions are 110 BCD 4.

If yes where can they be bought?
I purchased a Vuelta mountain crankset which came with steel chainrings in the same 44-23-22 sizes to replace the alloy rings on the same crankset you have.  Everything seems to work fine after some minor adjustment of the front derailleur.