There are a number of places and it is worth shopping around. Try Essentially Oils, Base Formula, Bay House, Materia Aromatica, New Directions, NHA Europe, Ancient Wisdom, Aromantic (for when you are feeling really adventurous and want to try making your own from scratch). There are probably many others that other forum members have successfully used. You need to be able to list the ingredients somewhere so it is helpful if you can get this info readily from the supplier.
Costs do vary as do texture and ease of mixing etc and you may find the cheapest doesn't give you the quality you would like to be associated with. Ideally you want somewhere you can get small quantities from to try or get a really strong recommendation.
I've mainly used Essentially Oils as the quality and miscibility are both good, they put stuff on offer quite regularly which may be of interest. They also send a regular newsletter which I find very interesting and sometimes thought provoking. However other than Aloe Vera Gel based products and my range of oil based aromatherapy blends I have stopped making lotions and potions.