I'm not familiar with the IMTB style. My mill uses NMTB 30 taper tooling and the cheapest place I have found it is through 800watt (seller) on eBay. If you buy from him be very very very patient and don't anticipate a response to any emails at least not on a timely basis. He's notoriously slow but he has eventually managed to ship my orders. Keep in mind it's Chinese and not domestic quality but decent for the price. I bought an er40 quick change setup with with 15 collets and the spindle adapter for under $150 including shipping about a year ago from the guy and several other items since. The only tooling related problem I had was with an albrecht copy chuck and NMTB30 adapter. The chuck was ok but the adapter was tapped for a metric drawbar. All the other NMTB30 stuff had standard threading.