I personally think that the best adapter is a 68k Mac running Laserwriter Bridge, or better still, the Apple Internet Router (which gives you zones!) and Appleshare Print Server (which gives you freedom from your desktop print spooler in classic MacOS). You merely need a Mac with localtalk and ethernet, and you can network your printer with any Mac. It will even work through a wireless router.
I would say that pressing an old machine into service is basically the easiest and cheapest option, even if the route taken in the free laserwriter Bridge, since you can likely find a Mac more easily and cheaply than you can find the adapter (i.e., most likely there are several already over in the corner). This option gives a disused machine a role in the world, and it works as well with OSX as 8.6-9.2 on your clamshell.
Do you have the memory upgrade in your LW4/600? That makes a huge difference with this model, and is well worth whatever the cost would be if you plan on using the printer for any length of time. Otherwise, postscript errors beckon with most any large file, whereas with the memory upgrade, they are eliminated. I purchased mine several years ago from a company at canadaram.com . They may have some left.