The mind map for Syntopic reading is provided in the PhotoReading book pg 112 (3rd edition)
The important aspect of Syntopic reading is your Central Purpose. I suggest you use what sources you have by reducing it to the 4 to 6 that are most relevant to your topic.
For information you don't have access to use the concept of mind mapping to do a brain dump. Write the Central theme or question in the middle. Branch out with mind probing questions. add the answers to the mind probing questions as they come up.
You might want to get some large art paper and tape 4 sheets together to make an even larger sheet and tape it to a door or wall for a couple of days. Add answers as you think of them. carry some 3x5 cards for notes or postit notes so you can stick them to the mind map when you are there again.
After a couple of days you can add combine with the Syntopic reading information you do have access to and you would be able to write something from that.
Don't limit yourself to Syntopic reading either. There is freenoting or rapid writing, image streaming, imagine yourself explaining a the answer to someone you know, who knows little about the subject (rather than someone who does, that's intimidating). Be sure to record (tape) while you answer or explain there will be some juicy bits for sure.
Alex