I've already shown one I made for my toddler, and here's a second one in toddler size (2T-3T size on my 18 month old if you're interested).
This vest's made from fabrics I pulled out of my stash, some black gingham and cream fleece. These fabrics are much thinner than the polar fleece and drill cotton I used in his other vest so it was actually easier to sew, especially topstitching across the bulk of the seams.
I also played around with the pattern a little to make a vest for my older boy. The original pattern goes up to a USA size 5T, I'm not sure what that equates to in Australian sizes but it looked just slightly on the small side for him (he's six and a half). In a nutshell I added a little length at the hem and a little width all over, which it possibly didn't really need, but most of all it needed expansion in the arm hole. I added about 5cm of length to the chest area at the point of the middle of the arm hole, keeping the neck as per the original pattern.
I let him chose the fabric, I thought the gingham was actually going to be his pick, but he went for the elephant corduroy and also chose the grey trim. It's got teal polar fleece lining and four black buttons down the front.
It's pretty generously sized so it should last a good while - its only March now and the weather will steadily cool through autumn and into winter and then all wearing of vests will be abandoned entirely when spring hits in September. We have trips to Melbourne and New Zealand on the cards this year too, which are perfect destinations for a bit of vest wearing.