I don't know of any website with this information - as you know, WLS people are in a category of their own with the complexity of vit/min supplements.
There is some variation with specific vitamin preparations - but let's try & keep it simple.
Your multivitamin should be taken with food
Your iron & calcium should not be taken together
Vitamin C helps with the absorption of iron
Any caffeine or the caffeine-like compounds in tea will reduce iron absorption dramatically (if you drink coffee in the morning - don't take your iron then!)
That should get you started. If you have more specific questions, let me know.
Danielle Halewijn RD