This question is brought up quite often. But first, why do you need it? On your boat pictures, I noticed GA reg. numbers, and if you do indeed live here in Ga, as far as I know, you don't need it. Half my boats don't have one, and I dislike having it on the other boats, as I disagree with it's horsepower capacity. :shock:
Anyway, as long as you aren't doing something obviously unsafe (65 horses on a 14 foot hard chine jon boat, or putting 6 adults in a 12 foot rowboat) no one will have any reason to care about whether or not you have a plate.
Here is a link to a similar question I asked on another board, before I learned about these.
https://forums.iboats.com/showthread.php?t=215557&highlight=capacity+plate
Going back and reading that, I sounded quite grumpy. Wonder what ticked me off that day.
Now, if you do still want one, I have heard custommarinelabels.com is a good place to get them, but the site is currently under construction, and unviewable. Now, I remember seeing a good place to get them, but cannot remember it for the life of me, and a google search rendered nothing useful. It may have been the aforementioned site, but I can't view it right now, so I don't know.