My experience is limited to the one I have been using for a couple of years https://uk.jackery.com/products/explorer-240-portable-power-station: goes all night even in bitter cold, recharges in a couple of hours from my off-grid solar inverter. I chose this one because a saw a comparison review of half a dozen or so, and this had the most consistent output voltage. A quick search suggests similar battery packs are widely available. Where have you been looking?
British Astronomical Association
Supporting amateur astronomers since 1890
