Sue, you can actually buy them at walmart, whole food stores, health food stores, etc. There are several companies now that sell whole raspberry leaves at large supermarket chains. I’ve only seen them at 2 walmarts.
They come packaged by a company called Alvita (in the big chains) or you can buy them bulk (& save big $$) at health food shops.
Here’s a link so you know what they’re boxes look like: