Vape Inc. do a few which are quite competitively priced like Toonz, and T juice and Vampire Vapes do concentrates of their popular juices like Red Astaire and Heisenberg respectively. Ideal for starting out mixing DIY, but some do have conditions that they are for personal use only, not to sell on...
chefs vapor do pre mixed concentates they sell there own brand plus t juice.
vampire vape have a few of there concentrates on sale this week just click on the sale section on there web site
Mom & Pops and T-juice are good old stalwarts. I like them because of their consistent results and are definitely not tightwads with regards to how much flavourings they are using in their blends.