You should go to those wedding photography shops first. In PJ i would probably ask you to go to SS2 where there are 2 big bridal gallery shops. Inside Sunway also has a briday gallery shop (dunno if it is closed?)
In KL the only shop i have went to is Dynasty formal wear in Jln Tuanku Abdul Rahman. The shop is in level 1 or 2 inside a building front of the cinema near Sogo. Its not in Pertama complex. I forgotten their rental rates. But i remember you need to pay RM500 deposit.
If you wanna buy, i can only think of Marks and Spencer in KLCC. Only they have tuxedo. But you would be paying about RM700 for the jacket and RM400 for the pants. You could buy from Bonia too if they still stock it off season. Prices should about Marks and Spencer range too. But tailoring would be cheaper. Or you could get a nice black suit from Kamdar at RM180. You don't get the satin front lapels and covered satin buttons. Geta bowtie and cummerbund set for RM99 inside Metrojaya in KL.
Just a suggestion though.