I'm afraid neither of the CD-ROM's mentioned by Günter actually have the units you need.
However the CD ROM called "Die Vereinigten Niederlande 1701-1714" by jean Belaubre & Claus-Peter Golberg does, and this can be cross referenced with C. S. Grant's "The Armies & Uniforms of Marlborough's Wars Vol 1". The CD is available from the source in Günter's post above.
Both regiments are listed on the CD-ROM as coming from the Dutch or United Provinces Army, and fought at Ramilles, Oudenarde & Malplaquet as well as many other smaller battles & sieges. They both come from the Province of Holland.
The "Nassau Guards" are in fact the "Blaue Garde" also known as the "Gardes te Voet" . Their "owners/proprietors" were 1701-07 Graf von Nassau-Saarbrucken, 1705?-08 Field Marshal Hendrik van Overkerk (Marlborough's great friend & ally after Eugene of Savoy) 1708 - 16 Baron des Veletre. It had 3 battalions. Uniforms are Indigo blue coat, red cuffs & linings, blue waistcoat, white breeches & stockings. Black tricorn, braided yellow, yellow buttons. Buff leather though shoes & perhaps scabbards & cartridge box may have been black. Officers wore same coat as men & wore orange sash over the shoulder. I think there may be other threads on these Forums re this unit - longer serving members may be able to help here
The second unit of Nassau-Walen is listed as I.R No. 21 on the CD (the unit numberings are not contemporary & do not match those in Grant's book) in the Holland Province list. Proprietors were 1701-07 Willem Hendrik Prinz von Nassau-Ussingen auch Nassau-Walen (also known as IR Nassau-Wallon, 1707-10 Andre´de Fournier and after 1710 de Marquette. The uniform is shown in the colour plate as Grey-white coat; red cuffs, linings, waistcoat, breeches & stockings; black unlaced hat, cartridge pouch & shoes;buff leather; tin buttons.
As far as unit flags go, I can thoroughly recommend those done by Stuart Wilson at Maverick Models
He does excellent versions for both these regiments as Nassau-Ussingen and Dutch Guards. He can print these on paper or silk and you can email to him letting him know just what size you want. I use the 40mm version - that means 40mm on the staff, not a modelling scale by the way. I also use the cavalry at 25mm size. I know these are a bit big to keep to real scale, but they look really good - Barry H introduced me to that concept
There are also flags you can play with through the Pike & Shot Society website.
Hope this helps.