I have a linear polarizer glass filter and would like to create circularly polarized light. What type of optics do I need for this?

To create circularly polarized light, you require a circular polarizer. A linear polarizer by itself is not enough to create circularly polarized light. A circular polarizer is really just a linear polarizer followed by a quarter-wave plate (also known as a retarder) that is at 45° with respect to the axis of polarization.

In short, you can either use a circular polarizer, or combine a linear polarizer and retarder film to create circularly polarized light.