You may be able to use a couple of DG419 or ADG419. I believe a DG333A or ADG333A is the same as a MAX394 (but not sure, you will have to compare datasheets)
It looks like the circuit on page 12 of the datasheet switches the cathode to -5V, thus providing 10V between anode and cathode. (+5V from the 7219 anode segment drivers & -5V thru the fets)
The motor will only draw as much current as it needs, whether you use 2 LR41's or 2 D cells. Adding a resistor will only slow down the motor. If you are concerned about excessive current draw due to motor failure, put a low value fuse in series with the external batteries.
The MAX232 is an RS-232 communication chip, why not try a MAX680 or MAX681 or an ICL7660, there should be schematics on how to do this on their datasheets.