In the US, there is a product called Neocalglucon which is a
liquid calcium supplement composed of calcium gluconate.  
It is a a clear, citrus flavored calcium supplement that I 
was able to give to my milk and soy allergic baby/toddler 
until he was able to take a chewable supplement.

Neocalglucon is an over-the-counter supplement but you will 
have to ask your pharmacist for it, since for some reason, 
pharmacists keep this particular product behind the counter.  
Not all pharmacies carry it and it may have to be special 
ordered.  It is not cheap but if it the only choice you 
have it is well worth it.

Preaching about not using calcium supplements and instead 
eating calcium rich foods is fine for adults but can be 
totally unrealistic if you are dealing with a typical young 
child's fussy eating habits. When you add multiple food 
allergies as many young children have, you have a very 
difficult situation to manage from a "healthy food" and 
"rounded diet" vantage point.   Let's not give parents on 
this list anxiety attacks or guilt trips just because they 
have chosen to use calcium supplementation for their children.
Many of us have enough other more significant health or 
medical problems to deal with on top of managing a milk 
allergy, and trying to convince a 
three year old to eat two cups of broccoli a day (or 
something else) is not something many of these parents
have the energy to do on top of all of the other health
related issues they may need to manage daily.

Tums has no aluminum in it and I don't believe that 
Neocalglucon does either. 

On the other hand, the suggestions about calcium rich food
sources are very helpful.  The suggestion about boiling meat 
bones with vinegar for a calcium rich broth is an
interesting suggestion which I will use and do appreciate
that information. However, even with using these kinds of 
great suggestions, there is a very real possibility that a
calcium supplement may still be necessary to meet a child's
daily calcium requirement.
    
My 2¢.

Lynda