My gynae recommended blackmores pregnancy and breastfeeding advanced prenatal supplements which includes fish oil. 1 bottle lasts me 2 months (2 tablets a day) and I get during bundle sales on Shopee off the official blackmores page. It was on sale for $64 for 2 bottles (4 months dosage) for 12.12 on Shopee.
kkh prescribes natal care plus, basic but sufficient. $2 per capsule