Being that you are coming from a tri background and are used to agressive aero bikes and that you want to consider continuing tris, I'd go for a traditional drop road bike with a taller headtube (less saddle to bar drop) from a shop that will work with you on stems and bars (change the stem out to something with more bend if necessary).

Depending on your tri bike it may be possible to convert, but most have very tri-specific geometry and are made to be ridden with the aero bars, so it may not be the best option.

A few brands are going with taller headtube options now, Cervelo comes to mind. Trek also offers two fit options (with different headtube lengths) on their Madones.

You may also want to consider working with a professional fitter with experience working with physical issues/limitations. It could be well worth the $150-300 to get their opinions on what bikes will work for you and/or have them help set you up on your current bike or a new bike. If you are in Colorado (or willing to travel) I have someone I'd highly recommend to you.