Where online can I buy knock off coach diaper bags?

If your friend has no clue "how expensive" her "dream" items are, you should allow her time to educate herself. If she wants "designer made items," you nor any of her friends are under any obligation to meet her demands. If in fact she knows what a Coach bag looks like, she should be able to spot a knock-off from 50 paces, so don't waste your money. If she's that particular about her things, consider combining efforts with a few friends and get her a gift card to a store that meets her standards. You won't find online shops advertising "knock-off Coach bags" or other counterfeits, which is against the law. What you will find are items that claim to be designer-made for bargain prices, which is a dead giveaway that these items are not authentic. Don't waste your money.