I used to buy Weider Mega Mass supplement from the Weider Pro Shop located at Shaw Centre. However, the shop has since ceased its operations. Fortunately, during my recent attempt to help someone in a forum, I have managed to find out and confirm that you can still purchase Weider Mega Mass in Singapore through Good Health Distributors Pte Ltd (parent company of Weider Pro Shop).
Their contact information and operating hours are as follows:
Address: 35 Tannery Rd, Ruby Industrial complex, #04-01
Tel: 6747-0635, 6747-0636 or 6743-0297
Operating Hours: Mon-Fri 9.30am-6pm, Sat 9.30am-1.30pm, Sun & P.H Closed