Did you consider the Workabout from Psion as handheld ? These machines are :
- not too expencive
- optionally equiped with a scanner
- can interface with PC via cable, IR and/or RF
- programmable in OVAL (but also C and OPL) which is a VB clone for the workabout. OVAL can handle the DBASEIII fileformat

Unfortunatly the OS of the workabout is EPOC and EPOC and DOS/windows can work together quit good but it's not the same.

I've been using them for some years (in some offline applications) and I'm quit happy with them ...