The most pictures you find on The Vinkhuijzen collection of military uniforms on the THE NEW YORK PUBLIC LIBRARY DIGITAL COLLECTIONS.
Look for the 1799 period.
When you type in Google: "Bataafse republiek" in Google-pictures, there is information also.
In fact for this period you can use French figures of this period to represent Batavian troops, the differences were small
Some infomation (in English ) is on the "Napoleon Series" website in the "Military section" under "Netherlands"
Good British troops for this period are fwe (Reiver also has some) but Eureka has great Russians
If you need some more information, let me know
greetings
jan