Not sure where to find these online,
however pretty sure you could do this in excel. Pick up a word list from where ever (there are loads around here and on the internet depending on the words/ type of words you want.) (for best results filter them into groups ie where you want to use 8 or 3 then work out what you want to replace. ie a where a is followed at, then do a find and replace ie find at and replace with 8t for creative or cre8tive or a simpler example freefall find free and replace with 3. For 3fall
After this add your tld of choice to the next column and use the concatenate function and this will provide you with a column of names to stick into your bulk search tool.
BTW not to sure how easy they would be to sell. Im guessing you have a set idea for them.