The best I can recommend is to browse through Osprey Publishing's catalog and see if there's anything that suits your needs. They're quite popular with the miniatures crowd.
I did a Google of "Islamic heraldry" and I don't think you'll find a non-fictional source. History has left us descriptions and architectural emblems, but some imagination would be necessary to model the field heraldry of an army. The introductory texts from the above search do give fairly detailed rules from which to derive something reasonably authentic looking. An author's note and several citations in the introductory texts suggest that this remains a valuable work on the subject: