It isn't horribly expensive to get a new gravity feed HVLP gun from HF which will perform better than the gun you have. I went through a couple of that type of touch up gun and prefer the gravity feed much more.
I went into the store with the intention of letting them talk me into a gravity-feed if I couldn't get parts for my guns. And -- nothing for the "Taiwan" one, or even for the gun that the guy thought it was knocked off of. He could have gotten parts for my DeVilbis gun, but would have had to order one in.
So I got the least expensive gravity feed gun they had -- I figured that way if it doesn't work I know it's me, not the gun. It's a Finex Sharp by Graco, and so far it works great.
Only one run, and that's a doozey -- but at least it's from me brain-farting and moving too slow across the surface, instead of me saying "oh, I'll just make it a
little bit thicker to speed things up".
The picture doesn't do it justice. One thing you can never catch in a photograph is imperfections in the paint.