Jeff;
I use kits similar as shown here except these are PSI kits.
Penn State Kit
But they also have identical looking kits for just $1.29 each and are quite satisfactory for this application.
I just use part of the kit. Don't need the brass tube and end pice . Those pieces will probably come in handy for something else some time.
The 7mm tubes are just a tiny bit longer than slimline pen tubes so a touch on the disc sander brings them right on. Nice to have spares.
At $1.29 for kits and a very quick and easy product to make, the selling price of $8.00 each adds up to a nice profit margin. It's little things like this that pay for the price of craft sale tables shortly after the opening time of the sale.
W.Y.