I have caught many fox, both red and gray, in cage traps from 10”W X 12”H X32”long and larger. One trap that has been used is found at
https://www.wildlifecontrolsupplies.com/animal/TLT108.html. I have even had good luck with the Havahart Model 1079-
http://www.havahart.com/large-1-door-animal-trap Many folks like Wickenkamp traps (
http://www.wickenkamplivetrap.com/) of appropriate size. There are many good makers of cage traps. GOOGLE SEARCH is a friend.
Since fox are omnivorous, many baits will work. I think meat type baits are best. Bones and skin from fried chicken works good, canned dog and cat food is good, canned fish is another choice. Of course, you will probably have to thin out the cats, opossums, raccoons, etc. before you catch a fox. Ripe persimmons and some other fruits are effective for fox and not very attractive to cats around here.