My feet and hands get cold before anything else when I ride my bicycle in cold weather. I also avoid buying bicycle specific clothing, preferring to use things I already have. Sometimes I buy things from the hunting section of a sporting goods department. Hunters need to stay warm in cold weather, too. My winter cycling shoes are a pair of walking shoes with leather uppers. They have more padding and are warmer than the canvas shoes I use in mild weather.
Step 1: Learn from the homeless
The homeless use newspapers to stay warm in the winter. I find four plies to be just about right. More plies do not really help.
Step 2: Tear a strip of paper
Tear a strip down a full sheet of newspaper so it is about the width of your foot.
Step 3: Tear again at the fold
Make two strips by tearing again at the fold.
Step 4: Fit around the end of the toes
Fit the paper around your foot so it begins just behind where you toes attach to your foot. Bring it around the front and over the ends of your toes. Then let the rest fall onto the top of your foot. These are the parts of my feet that get cold first. A little extra protection here makes a big difference. It helps to crease the newsprint where it goes over the ends of your toes.
Step 5: Prepare to push the paper into the shoe
Put your toes into the crease so your toes will drag the newsprint into the shoe.
Step 6: Drag the paper into the shoe with your foot
Push your foot into the shoe as you normally would. The paper will go in with your foot. Keep the paper from going far off to one side or the other.