I know that Magardsport and VGP both were selling the "proper" bushes, as David said they were pretty expensive and I think they were just the white ones, not sure whether that's clutch or brake pedal.
I used Oilite bushes in mine, without too much modification, just a little thinning down of the lip to make them all fit in the pedal box. I took the majority off the brake pedal as that's under less mechanical pressure. I haven't done much mileage in them yet, so I don't know how well they work.