As a few have suggested in the past creating a web based generator is probably the easiest way and as @
Devil said client sided generators are easy to crack since they have to make a request to a site to grab the accounts instead of having the accounts stored on your site in a web based generator! There are many source codes out there for a web based generator. Just find the bugs and glitches get rid of them style it to your liking and secure it and there you go! you can also hire someone to do it for you or find a business partner! Hope I helped :)