Loco2 certainly can sell you a ticket from Aachen to Schipol in one go, for Thalys+Thalys or ICE+Thalys or Regional+Intercity.
Here are the options for a random Wednesday morning, to give you an idea. Capitaine Tren seems to have
the same options as well for that Wednesday, but requires you to have a Thalys The Card as they only offer print-at-station in France or The Card
Have a play with both websites, and see which one's style you prefer!