Dr. Simmons is just about the only OMT source of questions I have seen on the internet. For a really good general questions site, try http://www.usmleasy.com
It used to be free, but you have to pay for it now. I found it to be an excellent, easy to use resource for both USLME 1 and COMLEX 1. although the questions were a bit harder than the real thing.
There's also Kaplan's Qbank (another pay site), but I don't know if it is COMLEX specific.
If you really want a whole bunch of OMT COMLEX questions, try Savarese's OMT Review book. There's a few hundred OMT practice questions in the back.
You can get thru Savarese in about 1.5 days. Fast read. Do all of the questions at the end of chapters, but be aware, there are errors throughout. If you know this well, you're set for 20% of the exam. Perhaps you will see more people gardening with LBP on Oct. 12th & 13th. Didn't it seem like everyone was gardening on the June COMLEX???
the green savarese book is very good and has 5 full 180Q tests in addition to the questions in the back of chapters. The only mistakes i found were obvious typos
this book kinda taught me not to blow off omm questions...very very good sourse for omm