Mike:
The pyrex or plastic rattles are probably intended to be inserted into soft-plastic lures, squidgies etc, but work well for large flies when tied into a braided mylar tube.

A Google search for "glass rattles for lures" will give you plenty of options, here is Barlow's offering for example. Plastic ones are more durable but harder to find.

Click here for a Rattle-Rouser recipe from Chris Beech, his article in the Australian "Fly Life" magazine a few years ago was my inspiration. The additional flash-tail in my tie adds size and bulk, and helps the fly 'light up' a larger patch of turbidity, making it easier for the fish to find in dirty water.