It's hard to recommend a vendor because there are tradeoffs with each one. For an Amazon-like experience,
Nexaph is good and ships from the US, but the cost is higher (sometimes much higher though they do monthly? prebuys). For trying single vials, I would suggest
Deb. She is in the US as well as resells vials from Nexaph and Uther.
SRY is a popular
vendor based in China, and I haven't had a problem ordering for delivery from their US "warehouse." I haven't ordered anything shipped directly from China yet since I am still paranoid about seizure, even though vendors normally reship.
Related thread:
triz-whats-the-average-mg-shipping