I have been using Zap! for years for putting my artwork on a variety of high-quality product. They always make sure the print and set up is perfect. I check every week for sales. Side note: They smell awesome.
My only gripe is the price because I’m Canadian haha- but *genuinely* a fantastic service!! The charms always come out great, I love how involved you are in the whole process, you aren’t left in the dark about anything, the customer service is lovely, and I love how you’re given an extra charm (if you’re only getting one sample) incase you lose the first!
Really helpful with clear, easy to understand proofs at the checking stage and the finished result looks fantastic!