Don't know what you're referring to, unless it's the 'fittings' the hoses go onto which may have a barb on them. I don't know what the plastic 'liners' may be. If any of the hardware you describe is 'off-the-shelf', the automotive supply guys and those handling truck stuff may have some air fittings and windshield washer parts that might work. Also, if not, GRS might have made those fittings in-house, which you'll need to contact them for unless you successfully cobble together parts you need which will suffice. Other guys on the Cafe site may have done what I think you're trying to do, so they may have more to offer than I do.
It the the brass nuts that are used to attach the air hoses. The plastic liners as they are called in the manual are used to keep the hoses from coming off once you apply pressure to the nuts. I will call GRS Monday, but was curious if anyone was able to buy something like this over the counter at a hardware store.
Bobby: Those plastic liners are called ferrules and you might be able to buy them made of brass at your local hardware store. I have found them at Farm and Fleet, Thiesens, Tractor Supply,etc. You can probably find the brass nuts also.
Those fittings are 'ferrules' that Tim mentioned, and come in various sizes. They do need some resistance, compression, and a proper fit to work right, so they may or may not work for you. If there's a pet shop in your area, you may look around for fittings and such for aquariums, and I had luck years ago on a project, although it differed somewhat from the use you have. There's lots of hardware out there, so I think you'll find something.
Thanks everyone. I am limited in my mobility to run all over town. I ended up calling GRS and they had them in stock. I even got a couple extra.
The journey continues!!! Sharpening is next once I get the Graver Max running.
This is my third time trying to learn. I have the time to invest into learning now.