Berg would be a possible Netherlands gain as it had been united with Holland in Louis' kingdom. You'd have to compensate Prussia but the idea of a Prussian Netherlands was for a while on the table, swapping the ownership of the South from Austria.
Berg? Are you sure? East Frisia had been part of the kingdom of Holland, but not Berg as far as I know.
Anyway if Belgium isn't part of the Netherlands, East-Frisia is the area the Netherlands most likely would get. Assuming it would get any compensation at all. Actualy it all depends on what happens to Belgium. I could see Prussia getting part of it (Luxemburg, part of Liege, maybe parts of Limburg), but certainly not all of it. Austria could keep it, but they didn't want it. France wants it, but I doubt people want to give it to them (assuming a Vienna just like OTL's Vienna). I could in theory see Belgium being split up between Prussia, France and the Netherlands. It would cost France something though, possibly Corsica, maybe the Alsace, Although both have a big history within France (which Belgium/Wallonia doesn't have) and France probably wouldn't want to part with it. I don't think there would be a calling for an independent Belgium, but it is possible although unlikely.
Back to compensating the Netherlands. As mentioned East Frisia is a good chance, Which would mean lesser sea access to Hanover.
Maybe the western part of Guyana, the later British part of Guyana, assuming the British want to give it up.
Other parts could be other parts of bordering Germany, but the Netherlands doesn't realy have a good claim on (most of) it. Prussia (and Hannover) would have to agree to losing it. It might want to give up the areas around Cleves or Gelders, if it would gain Luxemburg. Certainly it would not give up the Rhineland as Willem I's megalomanic idea was.*
If Hanover would be compensated somehow, i could see the Netherlands in theory gain western Hanover, if Hanover was compensated somehow. So if Prussia would give Hanover some land (like part of Westphalia), Hanover could give East-Frisia, Bentheim, Lingen and those areas to the Netherlands. The Netherlands also gains Cleves and prussian Gueldres, while Prussia gains Luxemburg, and Eastern Liege.
Still I doubt the Netherlands would be compensated. They might get a land bridge towards Maastrich (basicly OTL Limburg) and to Zeelandic Flanders, but if the great powers don't want to give them Belgium, they just gain the territory of the old Republic.
*There might be the possibility of Prussia gaining Saxony and thus forsaking the Rhineland (something the Prussians suggested, but the others disagreed with). Thus the Netherlands could gain the Rhineland this way. The problem with this scenario though is that the ruler of Saxony has to be compensated and the Rhineland is the most oobvious choice, so too bad for the Netherlands. Another less likely option would be Saxony gaining Belgium and the Netherlands gaining the Rhineland, but I doubt they would do that.