For those struggling with Syndrome, some tips I can recommend are to make sure you have 99% happiness and try to start or end your tasks that drop Syndrome tokens while a parade is going. I started working on Syndrome tokens late Friday night, and didn't get a single arm band or hat to drop all day Saturday. Starting on Sunday, I matched them with parades, and they started dropping more regularly, though they dropped in waves. Sometimes I got nothing, and sometimes I got 4-5 tokens at once. I also split my tokens between the characters. Mr.I, Mickey, Mrs. I on arm bands, Violet/Dash, Frozone, Mike on ear hats. I built the omnidroid city ASAP, and it dropped on average 1 ear hat every 12 hours, or every 3 tries. Monday night I got the last arm band, so I switched Mrs. I to ear hats and had Mr. I focus on tokens. Got the last ear hat this morning and welcomed Syndrome just after noon.
If you are trying to get Syndrome, DO NOT level up the other Incredible characters, as the tasks will drop lower value tokens instead of Syndrome tokens. I learned this the hard way and lost a whole day Friday getting more Mr.I tokens before I could start on Syndrome again. You can also skip the sidequests for Mrs.I so she can grab tokens. You only need 1 hour to welcome Syndrome, so you still have almost 1 day and 23 hours to grab those last few items.