I'm afraid the M&S gift card pkg is no longer available at Costco--at least at Costco.com.

Interestingly, earlier this year, it was taken off the site, and, after I emailed Costco.com customer service, it re-appeared the next day. At that point, I promptly ordered 5 just in case it disappeared again.

You might want to try this technique yourself and see if they similarly accommodate you.