Hi! you can get organic baby food easily at some bigger NTUC like the one at Serangoon NEX, or cold storage. Heinz has some organic stuff but I usually buy Bellamy, Healthy Times and Earth's best. There's a four seasons market at Farrer park (city square mall) which sells lots of baby organic food. I let my baby try fruits purée first n then baby rice, oats etc.
When baby first start to eat, they'll eat very little so be patient n dont't force her, just let her enjoy tasting new food. I intro food at 6 month coz stomach will b more developed by then. If you intro too early, there may b more prob like indigestion, cramp, constipation etc. mayb seek a second opinion on whether you should really wean baby so early. Can try looking for pediatrician instead of gp.