Well you can use the Wi-Fi based modems/dongles/routers/whatever they call it that basically connect to the cellular network and create a Wi-Fi network you can connect your iPad to (or anything else really).
A bit annoying given that it's one extra device to carry around and charge but if a "dongle" is what you want then I think it's the best solution.
A bit annoying given that it's one extra device to carry around and charge but if a "dongle" is what you want then I think it's the best solution.