Sometimes called sideplates or escutcheons

Here is a link that might be useful: Ashley Norton

I see what you mean. There is nothing that long, or else it isn't in the right material. You might try checking with a local machine shop to see if they could maybe fabricate something for you. You might also try asking at the link below
I wonder if you might be able to get the existing ones plated or something too.

Sue

Here is a link that might be useful: Home Decor Forum

Have you considered antique ones? Sometimes the designs on them - especially an Eastlake design can be pretty transitional/contemporary looking. I had a small collection that I was working on, to refit a house I owned, but I sold them. Many of them I found on ebay, All were billed as brass, but after polished, some were actually nickel.

Just a thought. :)