Look for tablets that run any variant of Windows (XP, Vista, 7). MS Access won't work on Android or iOS. I'm afraid no tablets qualify at the moment. So if weight is an issue, go for a netbook or an ultralight (but expensive) laptop.
But they might be coming: http://news.cnet.com/8301-17938_105-20031025-1.html is just an example. So better follow the news and you might be more lucky in half a year. Still, I'm afraid that not having a keyboard might be a problem, depending on the needs of the application.
Or reprogram the application in any tool that runs under Android or iOS (for the iPad).
My business is currently looking at testing out Verizon's Samsung Galaxy tablet, running the Android 2.2 platform. Our business uses a propietary software program based off of Microsoft Access, therefore requiring our technicians to carry around laptops. My question is this - is the Android tablet capable of fully operating Access? If not, is there a tablet out there that does? We're just looking to 'lighten the load' that our techs have to carry around with them going from account to account, and the tablet seemed like a viable option.