Open-source or cost effective DPS software

Hi all I'm looking to set up a DPS for a private company that operates EU funded projects, in order to help regulate the expenditure with external contractors. Due to the relatively small scale of the project the feasibility of paying a licence fee for some of the main players in terms of procurement portals is probably not going to be a viable option, and to be honest we are looking to implement as simple a platform as possible. Has anyone got any experience of any cost effective solutions for putting together a simple DPS? Something opensource or a platform that can be easily manipulated to meet the requirements would be ideal, although if there are any solutions which could be purchased outright for less thank £2000 that would also be a possibility.