Check on GravesRc.com or Bisson, they should have them. Im also 99% sure that pitts mufflers that fit the OS FX and OS SF .46 should also fit the TT Pro .46
And NO you shouldn't be worried about engine issues mounted sideways. The most important thing on any engine weather is mounted straight or sideways is to run it dry after done flying and use afterun oil or air tool oil to keep it from rusting.