I don't make custards, I mainly vape berry flavors, however, I can tell you where I got my stuff.
Wizards Labs
Wizard Labs is located within an hour's drive of my home. I did a bunch of research and made a list of what I thought I would need to get started in DIY. I called Wizard Labs and talked to a lady in the office. They don't really have a "retail" store where you go in and look around, make purchases, check out and leave with your stuff. They generally deal with internet orders which they ship out. However, they were willing to help out a guy just getting into it and told me to come on over.
My wife and I drove over with my list. When we got there (I had called again to tell them I was coming and what time I expected to get there) they had a Chemist waiting for me! Colin, the Chemist, talked to me about what I wanted to do. As we were talking, John, the owner of the business came into the lobby and introduced himself. He explained that he had started vaping to stop smoking and became interested in the process of making juice. With his chemistry background he began looking into the process and decided he could do it better than many of the companies that were supplying equipment and flavors.
John was so into vaping that he purchased starter kits for all of his employees who smoked! That told me a lot about him and his commitment to vaping. Colin vapes and also makes his own juice.
I whipped out my list and we started going through it. They told me that I didn't need all the beakers and flasks and fancy stuff I had on my list. Most just mix into a juice bottle. For measuring they recommended syringes and blunt tip needles which can easily be washed and reused numerous times. John mentioned that he wasn't much of a salesman as he kept talking me out of stuff he could have sold me!
To make a long story a little shorter, I left there with $112 worth of stuff. That included 500ml of 100mg nicotine which accounted for $53 of my purchase. I got VG, PG, a bunch of syringes in different sizes, blunt tip needles, about 8 juice bottles and ten different flavorings.
You can find a bunch of places to purchase your DIY supplies and equipment, but for me, with the service I received there, I will continue to use Wizard Labs.
Good luck, but be forewarned, it becomes addictive!!!