Old mean mate of mine[mean because he wont spend part of his millions on a decent shed] was re-assembling a cylinder head off his BMW R69.US [ not a dirt bike but it also needs parts] He dropped a valve collett down a crack in his verandah floor of his deralict house [which could benifit from a fire], said collet is lost in the fine dust of the ages.
Point is he contacted a purveyor of spare parts for these famous 'radial twin' machines and was told 'certainly Sir we can supply that for you .
Price for one valve collett only...wait for it 'that will be $70 plus postage Sir'.
Needless to say my old friend who I suspect still has his first pay envelope still un-opened was taken aback! Consequently that's one or more sales not likely for that WA Co.
cheers pancho