I made a google forms to hopefully make this process easier. If you want, you can put in your details here:
http://goo.gl/forms/OYBa7ajaC9. To find what shirts are available for trade and at what competitions look here:
https://docs.google.com/spreadsheets...it?usp=sharing
(I submitted a couple entries from this thread into the form already, just so people can get a basic idea)