The RAAF Museum in Point Cook, Victoria has a few bits and pieces of the triplane, as does the Australian War Memorial. The stunning new WW1 Aviation Museum in New Zealand (which name escapes me, but it’s run by Graham and Jane Orphan) has some of the wing fabric. I seem to remember reading the aluminium seat is in Canada, but I’ll happily stand corrected on that……
It’s worth bearing in mind that the last genuine Fokker DR1 was destroyed by Allied bombing during WW2, so we’re probably lucky that so many pieces of Richtofen’s triplane were souveniered when it came down and thus they’ve survived for us to study today.