Hi I always buy from open taste and they have a good selection. Some of the fruits and veggies come loose especially fruits. When you mean in bulk how many pieces do you mean? It is common for veggies to be packed in a bag or for fruits to be sold in a pack of three. But OpenTaste has many loose selections.
You can check out: https://www.purelyfresh.com.sg/ http://www.opentaste.sg/ http://www.redmart.com https://honestbee.sg/ If you have time in the morning, you can also go to the wet market. They do sell small quantities.
You can buy organic fruits and vegetables (per piece) at https://www.natures-glory.com/. They also offer organic grocery delivery in Singapore.