Newbie Question: US 100V Soldering Iron and Step-Down Transformer

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Hi there

I am looking to buy a a desoldering iron from the US that is 110V with
45W of power.

I am looking to buy an appropriate step down transformer for it.

Is a 50W step-down appropriate or do I need to get something more
powerful, say 100W or higher?

Is there a difference between certain step-downs, ie some are for
appliances with heating elements and some aren't?

Thanks for your help

Ric