Bikeberry.com sells them but just like the 32mm spacing, they're not all created equally so be sure you know which one you're getting, some of these have really nice wide transfers but there are also some that have the smaller slanted transfers as well as some are made to work with the 38mm cranks while others are set up to work with 40mm cranks.
Be sure to ask before you buy and alsonsee if you can get somebody to take anpic of the insidenof the jug so you can compare the ports to what you currently have, unless you know how to port and set port timing and duration be sure you're getting the right one.