If you have flat feet, bunions, or any other foot trouble, the idea of spending a week outdoors in medieval slippers seems like torture. One alternative is to make authentic-looking spats to disguise your modern shoes.
Here's how it works. Put on a comfortable old pair of sneakers. Take a large plastic bag, and put it over the shoe. If you want pointy toes, stuff paper wadding into a corner of the bag and position it just so. Then, wrap the foot around and around with duct tape.
Once the foot is all wrapped up, mark the tape where you want the seams to be. You can move the seams later by cutting and re-taping the pattern, so don't be too fussy. Cut the tape and bag away along the seam lines. You will have pieces that look like these:
If you are really gung-ho, you can study patterns for historic boots of your exact time and place to see where the seams should be. Mostly they go just where you would expect them to. After all, leather still comes in flat sheets, and feet are still foot-shaped. There are only so many ways it can go.
Lay out the pattern pieces on thin leather (or naugahide if you are really cheap), and add seam allowances where they will get sewn back together. Sew up the leather to make new uppers. Then, use a hot glue gun to attach them to the sole of the shoe.
Presto! Under a long dress, no one will give them a second look.