Try looking for a pillow afghan or pillowghan if you aren't finding anything for a quillow.
A pillowghan/pillow afghan/quillow is an afghan that can be folded into a pillow. Most of the patterns that I've seen for one have been crocheted using squares.
Here are a few links for some if anyone wants to take a look but I think you can make/use any square whether it's knitted or crocheted to make a quillow/pillowghan since the basic idea would be the same:
Pillowghan General Instructions by Priscilla Hewitt (crocheted sqs.)
Bond Machine Knitting - Pillowghan Patterns
Popcorn Pillowghan Square Designed by Julie A. Bolduc
I know I've recently seen some cute knitted dishcloth patterns that I think would be perfect for making as squares for an afghan or a pillowghan/quillow.