My favorite pen, the Parker 51, is a perfect fit in the hand, as a couple people have mentioned.
In addition, how about a Sheaffer PFM? The PFM is a light-weight pen, since it was designed and produced when fountain pens were intended for all-day writing. Later fountain pens are heavier. If you want a heavier pen like the PFN, Sheaffer made pens like the Legacy or Heritage, metal oens with the same size and shape as the PFM and with the same sort of inlaid nib that the PFM had. Last I looked, the new Sheaffer company was still selling them.
Ah. Can't find it on the new Sheaffer site, but it would look like this pen on EBay. I'm posting for a picture only, and not pushing this or any other example. https://www.ebay.com/itm/226100005452?itmmeta=01HW675SWFT4F088GMC2TBJ6KE&hash=item34a49c4a4c:g:020AAOSwAoRmIX0u&itmprp=enc%3AAQAJAAAA4L2FvYxTSRGiDarQUnt4nzzRhnmEkzVrU9%2Bt0uPf3apy8vB1Otg6REWWzCC1aJUqhqsqi4QwKAeH8%2BE%2FTymxCdLX2Zc4vHuVKinCwbl6JhYaDk%2FezeZC%2BxmGDcHIHk8OlyP5s37g1tkjfsin8jn8eKlStnXEWqD%2Bo3CtQ9DE4g%2FORcJYkepSC56J5VAC27wQHOYhA6FzaQ8ixnQYIUT2wUhOvrw1y8Km%2F%2ByQ4O1uL2%2FM2YhsNNOElL8DvJJz3uHTgIaxbi7FrRBnpZ4qJmUBxUyh9W2hs97Ujr81v60SA1sE|tkp%3ABk9SR6iel8fhYw