If you already have a Minolta meter I'd try that first, but an enlarger disk might be hard to find. And if you find one, it might be more expensive than a simple darkroom exposure meter, such as the one mentioned above.
I find the Minolta meter to be very useful under the enlarger -- after you determine the ISO of the paper you are using (with a simple step table test). The Minolta disc is white so you know what you are reading, and the hole in the middle is small, so you can meter exactly what you want (ex. mid-tone, clear film, etc.).
Of course which meter you use makes a difference. I use an Auto Meter II which shows the complete range of shutter speed and f-stops. So I select the f-stop first, and dial in the speed in the timer. If your meter is "shutter-preferred", where you select the shutter first, and it gives you the f-stop, I would find that less convenient.
