cytosine deaminase sources, please

[Larry Winger]

We've been having a difficult time trying to purify cytosine deaminase from
a kilo of yeast;  in fact, we've ended up with a sticky, yukky mess. 
Perusing the EC-enzyme database, I see that this enzyme is cloned.  Does
anybody have any idea of a commercial source of either the native or the
recombinant form?  Or failing that, a reliable recipe whereby we can get it
out of the yeasties?  We'd be much obliged -- seven verses of our favourite
Geordie song to the best informant, or not, if you should wish.