Me being me I didn't want to order some and wait (though you can get them from: Maiwa Craft Supplies) and I wanted to Be able to determine the lenths I wanted myself.
Well I was at "Scale Model Supply" a local hobby store and they had styrene model building supplies called "Plastruct" I grabbed some about 4 mm square and flexed it a bit. It felt resilient yet flexible. I decided to give it a shot.
I didn't really want to mount pins on the end as I have a habit of scraping my arm along pins that are pointing up at me. I decided to try the reverse idea. I heated a pin to red hot and quickly jabbed it down into the end of the Styrene. It cooled very quickly and didn't make it real deep into the rod (this is good). After it stopped being hot I then stuck the rod under the fabric and placed the end where I wanted it. Then I took some map pins (they're much shorter than normal fabric pins) and poked them in the ends. TADA! Poke free silk stretching!
Here are my lame-o diagrams: