I recommend 聖闘士 which can be pronounced as セイント ("seinto") and basically means "saint" or more literally "holy knight."

If you want to make it more phonetically similar to Saintly then... it depends what meaning you want for "~ly" (ri) - I can't think of any that sound cool off hand. Otherwise you could just have it written in Katakana so it'd be 聖闘士リ (seintori). (^_^)