A bucket on a string is the traditional way to apply anti-skate on a unipivot. Weight (usually lead shot) is added or subtracted to adjust.
Here's a Unitrac:
Sonus Formula 4:
A small plastic sewing thimble would work for the bucket. Heavy duty thread or thin nylon fishing line works for the string. You'll need some kind of rod or support to suspend the bucket. Some hardware stores sell aluminum rod. That's what you see in photo #2. This stuff is easily bent and you can attach it to the lifter platform (if it has one) or make a little base and set it on the armboard.
If you want the bucket on the inside of the arm - toward the record, attach the string to the back of the pivot housing or the arm wand behind the pivot.
You can even wrap it around the wand and tie it off. Just have it so it doesn't move around. Conversely, attachment in front of the pivot requires bucket to the outside.
You might have to figure out how to suspend the bucket in an upright position. If you attach another string across the top of the bucket, you can tie the main string in the middle. Heavy duty thread is easier to work with than fishing line. Both will work.
Once attached to the arm or pivot housing you need to adjust the length of the string. When the arm is on the record the bucket should be in the air, not sitting on the armboard like in photo #2. When the arm reaches the label the bucket should be near, but not stopped by the support bracket.
The reason the Sonus bucket in photo 2 is sitting on the armboard, is because the arm is all the way down - not being used at the moment.
The weight of the bucket alone will give a tiny amount of anti-skate. If you don't have lead shot, find some small hardware, like cartridge fixing nuts to add to the bucket.
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