Actually, you can use any iDEN phone for that purpose.  Best way to do so is to simply make one into a Boost phone and use the PTT only feature.  I think it would be cheaper for you in the long run (unless you plan on using international PTT, that is).

Otherwise, you will most likely want to mate any iDEN phone (with the exception of the Motorola i1) with one of those business plans (if you can get one).  At the moment that I'm typing this, the ONLY option that Sprint is offering is for one to guy a minimum of $30/month PLUS an additional $5/month for nationwide PTT (international PTT would be an additional $10/month more).

Leave it to Sprint to once again try to suck the life out of us Nextel Direct Connect users.