No slipcovers here but I have been playing with upholstery. I got the fabric for this one from Country Curtains; it was $30.50 per yard on sale for $3.99, and it's fabulous. They are sold out of 2 colorways, including mine, but they have it left in a neutral, which may be what you want. I have linked it below. I used the back side of this 'Belvedere' fabric facing out.

I also recommend Barn Fabric Center, as Gary usually sells his 'drapery' weight fabrics for $5.99 a yard and ships very quickly. http://www.barnfabriccenter.com/
His upholstery fabric is $6.99 a yard right now.

I bought the linen to re-do this antique chair from the Barn. Modelling it after this Restoration Hardware one for $1695. http://www.restorationhardware.com/catalog/product/product.jsp?productId=prod80194&categoryId=cat280016

Before -

During/almost after! Please try to ignore that awfully messy background.

I'll make a large down pillow for it from this 100% flax fabric from eBay. This was just a small sample one.

I can't recommend eBay for fabric enough, if you have the time to scroll through hundreds - thousands of options. I have bought so much fabric there, at incredibly good prices, as well as from FabricGuru.com.

Here is a link that might be useful: Belvedere Fabric