While I have a number of Jinhao pens (X-450, X-750, 601, and others) I have never really found one that my hand was happy with.
Recently, however, there has been a revival of Piston-filling pens from the Chinese market. The first was the relatively expensive Taiwanese brand TWSBI, a few years ago, and it has an excellent reputation on the FPN.
This last year has seen two models under the Wing Sung name - the 698 (better quality, ~ $20) and the 3008 (cheaper, ~$5) - as well as the Caliarts EGO (~$10).
The 698 and the Caliarts both hold about 2 ml of ink and the 3008 about 1.2 ml., both more than the standard converter of about 0.7 ml.