If it's just looking for an alternative to Plux-X, FP4+, maybe give Acros a try. I assume traditional grain since you are looking for a replacement for Plus-X so I don't include TMX or Delta 100. Acros is somewhat in between IMO, at least in look. Neither of these are Plux-X and will look slightly different, but a shot isn't going to succeed or fail based on being made on Plus-X or FP4+. If one would get the shot nicely, the other will too. Acros is a bit different due to the more significant difference in spectral response and reciprocity failure, the former making the look "more different" and the latter affecting low light.
This doesn't address development time, but just develop for as long as it takes.