I have the 3G Straight Talk "hockey puck" that does quite nicely for email and viewing rv.net. It works on the Verizon network. $15 for 1 gig lasts for a long trip with moderate surfing but no video streaming.
If you are looking at the 4G LTE versions stay away from the AT&T GSM version. I understand the Verizon version works but the speed is reduced. Either of them use the same data card, $15 for 1GB/30 days up to $50 for 5GB/60 days.
This is the one I use.