I've been working on an app which allows you to design Turk's head knots so they can be 3D printed. Recently, I released the very first version which creates Turk's head rings. It can be found here: http://knots.freakinsweetapps.com
This instructable explains how to use the app so you can order a 3D printed Turk's head ring.
Step 1: Find Your Ring Size
If you don't have a ring that fits, you can find your ring size by using a strip of paper. Cut a strip of paper about the width of how tall you want the ring to be. Wrap it around your finger and mark it with a pen. Then measure up to the mark and look up your size in the chart below.
Step 2: Dial in Your Ring
Go to http://knots.freakinsweetapps.com and click 'Get Started!'. If this is your first time, you may need to install the Unity3D plugin. Once installed you should see a ring with some sliders around it. Dragging the sliders will change the ring size and height of the ring as well as the density of the weave. When you've designed the ring you like, click the 'I Want This Ring' button. The ring will be uploaded to Shapeways and when it's ready you'll be redirected to Shapeways where you can order the ring. It can take a minute or two to process your ring. In extreme cases, it can take even longer. If for some reason you leave the page before being taken to Shapeways, you can go directly to my Shapeways shop and find your ring (it will most likely be the very last one, or at least near the end): http://www.shapeways.com/shops/freakinsweetknots
Step 3: Order From Shapeways
Once redirected to Shapeways, you can select a material of your choice. You can order plastic in a number of different colors, or you can choose one of the metals which include stainless steel, silver and gold plated brass. Once you've chosen a material, click 'Buy Now'. You can then click the 'Checkout' button from your cart at the top of the page. Fill out your payment info and shipping information and you're good to go!
Step 4: All Done!
Shapeways will create your ring and ship it to you when it's ready!
I'm actively working on this app, so follow me to stay tuned on its progress :)