How about anatomical images of feet, like the muscles? Or other illustrations of feet? Don't think it's strange. Human beings are gross when you really take the time to examine ANY part of their anatomy. Just don't think about it. How? you may ask.
Life drawing should be done in sets, like basketball drills. Do 15-second sketches of feet and you won't have time to be grossed out. 10-15 seconds, then 30 seconds, then 1 minute. Work your way up to 5-minute feet drawings. This is true for all parts of the body, and whole body poses.
I know it's rough. I've drawn some gross people over the years. I had a model that had a lot of piercings in a lot of interesting places. It would have been really off-putting if I had to stare intently at some of those parts of anatomy for two hours. Thankfully, life drawing is active and fast. By the time you've drawn that person 50 times in an hour, you've forgotten to be grossed out.
I really hope this helps. I've sure you can get it. Best of luck.