There are some datasets for Arabic alphabets but not specifically hand-written. You can find some typed or digitized letters that might also be useful for your work. Here are some links for the publicly available data:
1. This is a dataset that consists of 4,587 Arabic articles with a total of 8,994 images.
2. This is Kaggle Arabic Handwritten Characters Dataset. It is released for character recognition, however, you can definitely use it for segmentation.