You can buy in an FMF Q4 from the States cheaper than I can buy them trade from my UK supplier! But, that said, they are available in the UK.
The Motad is a lovely exhaust and has quite a lot more to it with every part in stainless steel including the sound-deadening gauze inside - see http://www.totallyttrs.com/#silencers
i have a rear exhaust from a wr250 which i have fabricated to fit the ttr250 fits straight on to the original center section and use's original hanging mounts