bought pic related off amazon, about 10 bucks. AKEOIL grease gun coupler. Feels very solid, but the jaws don't sit perfectly within the barrel like the pic shows - there's a bit of side-to-side wobble. Tried it out and some grease still leaked out which sucked.
Ended up going for the og lock-n-lube one because it was rebuildable, but I haven't tried it out yet. there's an aussie version for roughly the same price that's built by alemlube, but it looks more annoying to rebuild.