You will need to design your pins, then find a good jeweler and have them made.
The design is up to you. It can be something as simple as ribbons in your colors for new members and your letters for initiates, or you can incorporate symbols, gemstones, etc. As chideltjen said, your pin should be meaningful to your sisterhood. Check out other GLOs' pins for inspiration, but in the end you'll have to put together your own design.
My local had a simple badge for initiates - the letters in sequence in silver with an amethyst (our gem). Pledges got a ring with amethyst and malachite (our colors were green and purple). This was a deliberate decision on the part of the founders, to have a ring, since everyone else had pledge pins.
Hope this helps.
