There are definitely opportunities. Podiatry overseas, Podiatry medical missions...
One thing though, and this is a matter of personal opinion- I do not see any true value in mission trips. You go, work your tail off for a few days, take some photos, and then leave. No follow up, no aftercare- putting in stitches you won't be around to ensure they are taken out. Frankly, it's irresponsible. Again, matter of personal opinion- but the opportunities are definitely there.