Got a cheap and cheerful mini grease gun from Aliexpress, works great except it kept tipping over and I found it hard to squeeze.
Made a wider base for it, as well as finger flanges so that you could hold it like a syringe - makes it easier to squeeze and control to flow of grease.
The collar for the finger flanges is a tight fit. If it doesn't fit your grease gun try rescaling it 1% in your slicer.
Base will need to be glued on with two-part epoxy or something similar.
The author marked this model as their own original creation.