These 7 amp (84 WH) hard case LiFePO4 batteries are brilliant if your back can stand carrying a little extra weight. They come complete with bespoke charger. I have had two for over 2 years, still in good order. I can run an FT-857 at 50 watts TX power on at least 5 activations for 30 mins RX/TX before the voltage drops to the point where the radio turns itself off. Usual auction site:
73 Phil