There's a creative obelisk spawner in NEI, however it doesn't come with a sinister node, so you'll need to stick a sinister node in there between the pedestal and actual obelisk.
Thank you, and sorry for all the Obelisk talk
This is for anyone else that is have as much trouble as a few other and I have/are in finding a thaumcraft Eldritch Obelisk in your world.
1st you can use the Sinister Loadstone to hunt, well sinister nodes. That is what is under a Obelisk, but you will also be led to totems, and sinister nodes themselves.
2nd I did some testing and found out a few things. If you load up another world to hunt for an Obelisk and find one you can make a schematics of it then transfer it to your world. I made one and was able to export using Mcedit then import it to my world. I also tested if it still would work when activated, and it did. I also have the Obelisk.schematics if someone wants it, I will set it up later to share it.
3rd I tried the creative Obelisk spawner, however as stated by thephoenixlodge it does not add the sinister node. Without it the portal will not work(you can not activate it. The bad news is even if you find the node(they are easy to find) you can not place the creative obelisk to use the node. I haven't tested if it will work next to it instead of between the pedestal & obelisk. If you are familiar with the middle mouse click while in creative looking at an item/block you add that item to you inventory(copy it). I did test if you copy the obelisk, and the pedestal under it then place the pedestal under a sinister node and the obelisk above it that works. Then all you have to do is put in the hours of work to get everything to you need to activate it. I hope that helps.