Hi there,
I mostly do just DIY and yes,
Perfumers Apprentice is a good place for flavor.
Lorran candy oil is good, and there are a lot of recipes using them.
Cappella is another good source, and awesome customer service.
Lastly, you can get
Flavourart from various sources here in the US.
FreedomSmokeUSA being one of them.
I use all in my DIY mixes and have no particular favorites other than the tobacco flavorings for which I use the Flavourart.
There are other manufacturers of flavors, these just happen to be the ones that I use. Hope this helps
Regards
Jim