If you go on stallionsonline.co.uk and select 'arabian' in the breed box, you will find some black stallions listed. If the stallion is homozygous, it does tend to be mentioned.
Mahalla, straight Egyptian. AH Kuda, stunning and multiple winner in the show ring. In Suffolk Lisa Dunn has (or had) one, can't remember the name. In Norfolk Have to do the horses now but I am sure others will add some and I will have a think.
There may also be some new young boys on the block!
I have a homozygous black boy, but he won't be used til next year. Have you looked at EssJay arabians, she breeds blacks and some of her boys are homozygous I believe.