It grows in my garden. I was pulling it out today. That suggests it is opportunistic, and could be anywhere suburban.
I fed it to the chooks.
I'd check the attributes in way of what it looks like -- and walk your neighborhood.
Here's what it the looks like:(LINK)
Any weed like that would require some moisture -- so keep that in mind when hunting for it re after rain, in hollows,maybe in shaded places... and well watered gardens or gutters.
And in mine. Don't know specifically about 'wild' chickweed. It's an exotic so is wild or feral anyway. If you live near enough to Deception Bay you are welcome to some of mine (need to check first if it is growing now). It's usually prevalent in the cooler months - it self-seeds and comes up when it's ready.
So if you're sure you know what it looks like, as suggested have a gallop about your area and harvest any that you see.
And there's 'chickweed' and 'tropical chickweed' that I know of around here. Dave's link is to 'tropical chickweed'. This link is for 'chickweed'. Two quite different plants botanically. Which may or may not make a difference to the poultice.