plain yogurt... cold storage, ntuc, carrefour have them. there are fruit flav. & plain ones... get the low fat plain ones.
Acidophilus supplements... well, not too sure about these. but if you could take 'natural food source that contains 'Acidophilus agents' isn't it better...
yalkut, vitagen, culture milks have good bacterial too, but again get the low/no sugar ones.
cheese - errr not the kraft cheese but medium/soft gourmet cheese like brie, blue vein, etc... they have rich bacterial too. (but fattening lah, cannot every time eat)
hmmm... 'Acidophilus agents' are also found in carrots, soybeans, rice starch (whole grain/purewheat), etc...
as for Acidophilus supplements, maybe you ask your doctor best... b'cos natural food source are easy to digest, but supplements are minierals, so can't comment on them.
take care