I have 2 options that work most of the time: 12ft.io and archive.ph. The URLCheck rules are:

"proxy it with archive.is": {
    "regex1": "^(https?):\\\/\\\/([\\s\\S]*)$",
    "regex": "^(?!.*(archive\\.))(.*)",
    "replacement": "https:\/\/archive.is\/newest\/$2",
    "enabled": "true"
  },
  "12ft.io.": {
    "regex": "^.*$",
    "replacement": "https:\/\/12ft.io\/$0"
  },

This basically brings up 2 buttons on the urlcheck sheet an I can pick either to proxy it.