Be wary of any gear that has a high collar, make sure it fits under your outer gear. If a zip together two piece suit, try that too.
Also, if you buy a heated item powered from the bike and you wear a one piece oversuit, you'll need to get the lead in somehow. If it has a two-way zip, that might be an option. Otherwise, a hole in a pocket inner. For my one piece, I made up an extension lead.
[Edited for clarity ]