Agentless patch level scanner to assess small acquired companies

The company I work for recently acquired 5-6 smaller companies with < 300 windows clients each, and none have central patch management set up. I have been tasked to visit each site and conduct a IT security review, to include patch levels of all clients.

Would anyone have a recommendation for a quick, agentless patch level scanner I could travel to all the sites and quickly deploy to get a lay of the land? (does NOT have to be freeware, I have been given a small budget to work with)

Thanks in advance, appreciate all the great info I've been able to get from this site!