Bolster-ing the Day Bed

Our home office doubles as a guest bedroom, thanks to a wrought iron daybed we've situated opposite the desk. My vision for the bed was to disguise it as a sofa so that it could be a cozy place to read in the office or a resting place for a guest. So far it has successfully accomplished both tasks but I'd like to bolster the sofa quality by adding more pillows.

I'd love to take it from just so-so:

... to so-so lovely and relaxing! I mean doesn't this just make you want to grab a book and get cozy for an afternoon?

As luck would have it, I found myself at the Pottery Barn Outlet in Leesburg, Virginia and happened to see bolster pillows on sale. I found two, 10 x 27" bolsters that were marked down an extra 30% off their already discounted price. I think they retailed for around $30 originally, but by the time I got my hands on them, they were just $14.00, yay for me!

Adding bolsters to either side of the daybed mimics the look of arms on a sofa, perfect! Now that I've found the perfect pillow inserts, I am in search of matching pillow covers. Why do I have the feeling this will be like finding a needle in a haystack? Anyone know where I can find simple, white bolster covers for a 10 x 27" pillow? Please, do tell!