I too was a bit alarmed recently to read that most vitamins contain GMO products such as corn. I like Solaray. I lot of their products are organic and thus also GMO free. :)
Dr Mercola's Whole Food Multivitamin PLUS tablets (240 per bottle).
Do you mean synthetically made? Technically all vitamins are chemicals. If you have concerns about consuming synthetically compounded vitamins, probably the easiest thing to do is google a trusted resource for dietary (food) sources of the vitamin you're looking to monitor in your nutrition and make a conscious effort to consume more of those foods.
Generally speaking, in industrialised countries, we get what we need from what we eat with no need to supplement. Of course, around here, many people have deficiencies their doctors had advised them to supplement (B12 and D spring to mind among this group), so this may be a little bit trickier as it may be difficult to get the amount needed to rectify this in food alone. I would speak to your doctor about this.