NASSCOM has an initiative e-Procurement | A NASSCOM initiative which captures tenders for various government projects in India. You may want to refer that.
Do note that most reputed organizations have a transparent mechanism to source work and typically release a RFP. For e.g. Banks in India quite regularly release RFPs for data entry work. http://www.sbilife.co.in/sbilife/images/File/documents/RFP_Outsourcing_of_Data_Entry_Scanning_other_decentralized_activi…
One will find many such RFPs.
In addition there are specialized portals e.g RFP, Request for Proposals – Government RFP, RFPs, Bids, Tenders, Contracts, Solicitations from USA, Canada, Australia, … which collate work globally.
Whilst there are specialized consultant firms who provide work for a fee, I would recommend proper due diligence before you do business with such firms.