evenor

fromjapan, buyee, remambo, and aduma-san  

I use Zenmarket since they have a flat fee of 300 yen including free consolidation. Aduma is really good, too.

Zenmarket is top pick for me. 45 day warehouse holding time, 300 yen flat fee (which they occasionally reduce during promotions), and free consolidation. Haven't had much issue with them over the years and they're fairly prompt if you ask questions.
 

I sometimes use JPN-depot as well, as the charges are similar, but you have to pay for consolidation and they're a bit slower on purchasing things. One plus with them is that they'll buy from certain places like Mercari, which Zenmarket no longer does. Also, JPN-depot doubles as a Japanese address that you can send purchases to, so if you can read enough Japanese (or use Google translate for a checkout process), you can potentially save a fair chunk of change by making an order yourself and having it shipped there rather than paying 300+ yen per item you want.