Sizer, who was named managing director of Pakready in August 2009, recently left the packaging prototyping systems firm following the successful re-launch of its eponymous product.
Wifac Group chief executive Piet de Haas said: "Derek will be instrumental in building and maintaining our export business in the UK and Ireland.
"We are very pleased to have this opportunity to work with Derek and we look forward to future success."
Sizer added: "GPS is a solid company with good heritage and excellent technical support and warehousing. They have some very competitively priced thermal, violet and analogue plates as well as DuPont proofing and other products.
"My intention, over the next weeks and months is to set up a small number of key dealers in the UK and Ireland. I'm in discussions with some and I'm open to talking to others. With Ipex coming up it's a great opportunity to get things moving."
GPS, which is the export business of Netherlands-based Wifac Group, offers various systems and consumables for the graphic arts market including a complete offset plate range, blanket wash rolls, printing inks and DuPont proofing systems.
Sizer's career in graphic arts includes appointments with Hell, Harlequin and ECRM, amongst others.