Samloyal23
Adventurer
I would just just reskin the descriptions of an existing construct of the appropriate CR. Modify a few minor abilities to be more thematically appropriate if necessary. There are a ton of 3e monsters so there is no real shortage of existing construct statblocks if you want.
But part of the fun of the game is filling in gaps by developing systems to cover things not in the game already, answering questions like how much water and fuel a steam golem needs to function, how long can you fight in steam powered armour, and other things you need to steam power rules for so you have to homebrew.