The mention of silk for preventative health made me a little curious, so I went a looking for ideas for finding silk:
http://www.amazon.com/Silk-Sleep-Sack-Blue-%252884x36%2522%2529/dp/B00102V3IUI've wanted to pick one of these up for years, just for the material to make something else with.

(In some instance repurposing ready made bits saves money)
Here's the blurb from amazon:
[quote/] Product Description
The Silk Sleep Sack helps add 10-12 degrees to your sleeping bag keeping you warm on chilly nights. Plus it's ideal for use as a stand-alone sleepi sack when staying in hotels, hostels or anywhere you sleep. Silk is a natural and breathable material and provides a luxurious and comfortable sleeping environment. Features:- Weights only 5 ounces- 100% silk - Waterproof stuff sack included - Pillow compartment included - Side / top entrance - Use in any style sleeping bag - Ties included on each side for a snug fit Specifications:- Holds: One- Weight: 5 ounces- Dimensions: 84" x 36"- Attached stuff sack: 5": x 4"- Color: Navy Blue
[quote/]
This item has a good rating and isn't too expensive. Watch out pricing silk though. If a fabric is advertised under "China silk" it could be polyester, you'd need to double check.
Another good company to purchase silk by the bolt:
http://www.dharmatrading.com/silk_fabrics.htmlIt can be more cost effective to buy by the bolt and split the total + shipping between a group of people. Dharma Trading has a good rep and does offer swatches
so you can pick the weight of fabric, and yes, they do ship internationally.

If you are looking for a good bulk deal, they have them. (They also have scarves cheap)