What you're speaking of is a short code. There are "shared" and "dedicated". Dedicated start at 15k and top out around 30k per year. They also take up to 60 days to set up.
If you get a shared one which is the cheapest option. Try TextMarks or Mozes.
Do remember though that you must “Agree not to transmit political marketing (news is acceptable), religious, pornographic, prostitution/escort, gambling, hate, alcohol or drug related content." Yet Playboy has one and there's a couple church ones too.
Also, you've go to remember mobile campaigning is only going to get stricter. You may just want to get a cell phone with a data only plan and a dedicated custom number that's witty or easy to remember.
