ummmmm you can buy ebay if you are freaking insane... what I would recommend personally is go to a police supply store. I don't know if you have them up in Canada or not. Go there and get properly fitted for a vest. Often times uniform supply stores also carry vests. You can buy a generic vest any where but in doing so it probably won't be comfortable and may not fit you properly. Being as you are a woman the cut of the ballistic panel will be different then a male. they are considerably more comfortable then wearing a male cut vest.
Expect to get groped a little in the measurement process. they will measure around the fullest part of your breasts and back. then just under your breasts to obtain proper contour. Some may or may not obtain your cup size. they will measure your waist. they will measure from your belt to approximately your belly button both sitting and standing. they will measure your back from your belt to about your shoulder line.
a custom fit vest is far far better then anything you can buy from ebay or galls. if you are wearing it as a part of your uniform I suggest it. If it is a manditory part of your uniform they the company or agency you are working for should foot the bill or atleast part of it. If not custom is costly and will run you any where from 650 -1500 dollars in American currency.
remember this is my personal suggestion. I wore one every day for 3 years this is the way to go. if you do buy used. check the expiration date. they are only good for 5 years.
http://www.body-armor.com/femalecentennial.php
I used to sell vests for that company. amazing stuff. I am partial I have both a concealable and tactical vest from them. Not cheap but it is one of the best companies out there. oh and for your information. Ballistic panels are all made out of the same material so when you shop around you are looking for comfort of the cut and the quality of the carrier. Get multiple carriers as well. for more ask