A lot of folks go with the NEJE lasers. I have two.
The original is a 1500, which is fine for pen barrels. The problem is finding the rotary adapter for the 1500. It's small. Restricted to a 1 5/8" square area. The 1500 is usually around $100-$150.
The other NEJE I have is the 3500 watt. It is the general go-to for engraving. It will engrave up to a 6" area. There is a rotary adapter for it. The adapter is usually in high demand. The 3500 can be upgraded to a 20 watt, but if you are engraving and not cutting, you wont need the 20 watt. The 3500 is usually around $200-$280.
In either case if your buying one used make sure it's the Master 2S. The older version of software is no longer really supported. I bought my 3500 used. Is wasn't the Master 2S. The upgrade ended up costing me $125 or so, since the laser head for the older series 3500 will not work with the newer Master 2S series.