Where can I buy Iron Rosettes for Fence Project

Ok, did some digging ...
Bunch of stuff

First if you like these particular Rosettes
This company does offer FREE US Shipping
So if you live near the Border then using a US Parcel Drop Address
And going over to pick up self clear customs is by far your cheapest option

With the border closed now for Coronavirus
Things are a bit different,

You can use a US Parcel Drop Service that will HOLD your items (no charge or a fee per day / wk / month)
Or a Service that also offers up a PUSH North option

Don’t know where in Canada you live
As you have no locator in your RFD Profile
(As an RFD Newbie ... You really should amend that ... it goes a long way here on RFD when this is a national website ... and circumstances differ so greatly ... just put in whatever ... could be Town / City - Region - even Province (Mine says Eastern Ontario). But it goes a long way to understanding where you are coming from or dealing with in posts like this one ... big difference say between your living in the GTA vs Iqaluit)

But ... around the GTA a Co called CBP is very popular ... Cross Border Pick Ups
They have a PUSH TO Warehouse in Mississauga

There are similar services for places in Southern BC, Eastern Ontario ... and maybe Quebec & NB

The manufacturer you are looking at is Old West Iron, out of Idaho
They are a Blacksmith Forge
The items are Rosettes

As such, you can find other Blacksmith Forge Services that also make Rosettes
I found this Co .. AIDI = Architectural Iron Design in New Jersey = https://www.archirondesign.com/
They also ship to Canada

Likewise you’ll find Blacksmith Forges here in Canada too
Most offering up the option to do Custom Work
Including hardware like fasteners, hinges, etc

Just GOOGLE ... Canada Blacksmith Custom Hardware

Personally ... I would be giving this task to a fellow Cdn craftsman (preferably someone local)
Esp in these uncertain times