Buying sim card in IAH as arrival

Hi,

I searched the subreddit but couldn't seem to find an answer to this question.

We're travelling from Europe to Houston this week. We need to buy a prepaid SIM with data asap. Does anyone know if this is possible in the airport itself?

And maybe on a sidenote, what's the cheapest way to get downtown and how much would that cost?

Looking forward to visiting Houston!