is the form often used in research.
Natural Factors, WellBetX, Cinnamon, Extract 20:1, 150 mg, 60 Capsules
Doctor's Best, Best Cinnamon Extract, 125 mg, 60 Veggie Caps
both are quite reasonable at IHERB. I use iherb for cheap shipping to uk.
You may find cheaper amazon/google depending on discounts/shipping where you live.
Code WAB666 saves iherb newbies $5 initially.