HI there and welcome to the community.

I'm surprised that you haven't been able to find any.  There are several places online that sell apparel, I'm sure you could find something. 

However, please be aware that it is not proper for lay people to wear sangha clothing.  Unless you are trying to help a sangha member (i.e., an ordained monk or nun) obtain the necessary clothing, or you yourself are sangha, you should not be wearing the robes. 

LozangK
Beliefnet Host, Buddhist Teens