Try HB Bearings, 01484 665116,
www.hb-bearings.com, email sales@hb-bearings.com, part number is SKF 441933E but they are no longer available from SKF.
I had one from them last year - the price is not low but the quality appears to be excellent.
Steve Hall did a conversion to take a standard bearing but by the time you have paid for the machining you are not far off the cost of buying the standard part. Steve is handy with a lathe which I am not!
As Robin suggests, check out the ME site - the above details are on the Forum there.