Custom Currency Switcher

This technique was used on the Tomorrow's Modern Boxes, and the Knife Party site.

1). Open currency-switcher.liquid

2). Replace all of the code with:  

<div id="currency-selector">
  <a class="tmb-currency currency_current" href="/"><i class="fa fa-gbp"></i></a>
  <a class="tmb-currency" href="http://knife-party-eu.myshopify.com"><i class="fa fa-eur"></i></a>
  <a class="tmb-currency" href="http://knife-party-us.myshopify.com"><i class="fa fa-usd"></i></a>
</div>

Replace the links with the appropriate site and apply the currency_current class with the current store.