For antennas mounted directly to the HT, I’ve had very good reports on numerous summits using a Diamond RH770 telescopic (half-wave, radial-less, 93cm extended) even compared to a 5/8’s dipole on a 3m pole (and much quicker to deploy and stow away). The spec claims 3.0dB gain on 145MHz.
Before it fell apart, I also had a Chinese ‘770 clone [at about one-third cost of the Diamond] with a SMA-m connector that mated directly with the SMA-f on my Yaesu FT1D so was mechanically sound. The Diamond one seems to be available only with BNC and twice recently the SMA pin on two BNC-to-SMA adapters I used broke off mid-activation (presumably stressed by the antenna swaying about in high winds), now replaced by an adapter that sits snugly on the HT.
73 Andy