David,
IF you have the Vixen thread on your drawtube, you can use this and then use 1.25" diagonal and EP's:
http://myastroshop.com.au/products/d...sp?id=MAS-007A - most of the Japanese early refrators did, except the Unitron/Polarex (which means some Tasco too).
I use one on my 1960's Yamamoto - screws on the drawtube, then use 1.25 diagonal and EP's.
Failing that, there is someone in the USA that makes it, or I have a machinist friend in Brisbane (who is an astronomer) who'd make you one up for a small fee.