You can get back plates that are shorter than standard. But one of the things that we covered in my DIRF class was that the same backplate, when properly adjusted fit a 5'2'' tall woman and a 6'5'' man.
Going to a shorter backplate may also adversely affect your ability to clip off stage bottles etc, as it changes the 'standard' distance from the shoulder D rings to the waist D rings.
Before deciding you need a shorter backplate, you might do well to find some that you can borrow to try on a dive. Keyword here is "dive" as it is hard to determine how well the actually fit just trying it on land.
