Mindtrain mufflers are very hard to come bye.
Last time I spoke with Fred Matsumoto (MindTrain) he had 1 pair of his mufflers left (I believe they were the later model "L" mufflers, straight tips versus upswept). This was almost 7 months ago, so he very well could have sold it, but you could give him a try.
I have his contact info. if you would like it. Just PM me.
BTW, these mufflers aren't cheap