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The Amazon one is decent for small sissies, though when that clitty gets hard, its not great.
The pins...well, the pins are crap, in my opinion, and the fit is far from perfect, but to get a good fitting one, you'll have to shell out some money for them.
That said, I would reccomend buying something along these lines and modifying it for a bit more long-lasting comfort. Taking a hobby knife along the corner to create a rounded bevel for the ring, drilling a small hole for the side pins for a more secure fit, etc.
Its a good one to start with, but I personally recommend trying it out to see if chastity is something you like, and then upgrading from there.