IMHO there's only one type of grease gun worth buying, the Swiss Wanner. Not cheap at nearly 80 quid, but it will do the job perfectly for years without breaking or leaking. I've fitted a flexible hose onto mine, it's not really necessary but I put it on one day to try out and have never found a reason to remove it.
https://www.cromwell.co.uk/CTL5404512N
