Acer (Benq) doesn't post drivers according to the model number found on the backside of the scanner, they posted them according to the model number found on the top lid of the scanner. ie: 640p, 610P, 620U, 610S, 4300U, 320U, etc.
Your other choice at finding a driver would be to use our [url="members.driverguide.com/index.php?action=search&sm=e&qtxs=ndz&from_ums=1"]Driver Search Wizard[/url] to check for it's existence in our driver database or use your favorite search engine to search the internet.
Either way, you need to know the number that's posted on the top lid in order to find a driver.
This is what the rear label looks like:
This is what the top label looks like:
If you check previous threads by using the Search this Forum
button/link at the top-right of this forum, you might get lucky.
You can find drivers on the BenQ websites: