I've just done this research - I looked at all the ingredients and when there was a difference, say in calcium, I looked up what the word after meant and determined what impact it had on the vitamin itself. I used
http://www.luckyvitamin.com/
and here's the alternatives I came up with:
111711
Bluebonnet Nutrition - Calcium Magnesium Softgels - 120 Softgels $15.96
52783
Nutricology - Potassium Citrate - 120 Vegetarian Capsules $7.63
108523
Good 'N Natural - Omega 3-6-9 Flax, Fish & Borage Oil with Evening Primrose Oil - 120 Softgels $8.97
101552
Solaray - Spectro Woman Multi-Vita-Min - 120 Capsules $20.96