I've not seen on ebay for a few months now, as I've been scooping them up when they've been available.

I did find an indian manufacturer who listed them in ER form, but that's as far as I got.
Chinese suppliers wanted a copy of the relevant BT35 standard, as they only seem to do 30/40 tapers.

Regardless, you were looking at a minimum order quantities of 50 or 100 to get a batch made.