I like the Poke-a-Dots sticky thimbles.
http://www.jillilystudio.com/shop/No.../PokeADots.htm
Also, wanted to add that I just got a set of the plastic Thimble Lady thimbles for Christmas. I measured & came up with 5.4mm according to the instructions. A Medium size says "5.3cm" and Med-Large says "5.8cm". Here are photos of each of the thimbles on the finger I measured (middle finger). I must say that the one disappointment was that it talked about that it would cover over my knuckle, but really unless I push it way down on my finger, it does not cover the knuckle. I guess it depends whether your fingers are long like mine or short like Liuxin's.
[ATTACH=CONFIG]539585[/ATTACH] Small-Medium
[ATTACH=CONFIG]539584[/ATTACH] Medium
[ATTACH=CONFIG]539583[/ATTACH] Medium-Large
[ATTACH=CONFIG]539586[/ATTACH] Large