recently purchased from Brownells, through a local FFL. no problems at all, very quick transaction.
I'd think any of the large firearms retailers would be reliable. just be sure to read the fine print about shipping to Hawaii, FFL fees, and FFL transactions. That's incumbent upon you, you can't blow that off.
for Gunbroker, be sure to read the fine print about payment methods, CC fees, your chosen FFL's license being presented, and shipping to Hawaii. how many mags included. is it a stock picture, or actual pic of the actual gun. and whether they have lots of "+" ratings, read some of their reviews, most recent.
normal caveat emptor.