I get my Nicotine/VG/PG and most "regular" flavors through Denkat.
They have the best prices I've seen anywhere for Nicotine (I
buy 100ml/100mg) they also deliver.
pcrus .ph is their site to order from - their dedicated ecig site has been down a while.
You
can get VG in a pharmacy (Pure Glycerine) but not PG - Apollo Glycerine is the one I get when Im stuck and its available in
most larger Mercury stores.
Some Baking Supply shops may have PG as its used in cooking muffins n' stuff.
Honestly though its easier and more cost effective to juts buy a litre of both PG/VG and lots of Nic in the one place and have it delivered together.