The site that used to manufacture this tablet has been under construction for 10 years, I am guessing there will be no driver updates. VisTablet Penpad uses a WALTOP chipset so if you click the device ID for this tablet there will be other devices that are same and share the drivers.
VisTablet USB Driver
File: 2014_windows_vistablet_V5.05.zip
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VisTablet User Manual
File: New Manual of VisTablet PDF Version (Final).pdf
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Active Area: 6.0 x 4.5" Pen Sensitivity: 1,024 Levels Resolution: 2,540 Lines Per Inch (LPI) USB Connection