you can get them from puretime:
http://puretimewatch.com/product/new-arrival-pam050-a7750/
and trustywatchguy but their website seems to be dawn...
I am also willing to get one myself
here are the mods that you can do in order to get a really nice pam (I found this on an old thread so maybe it is not possible anymore to get the parts needed)
1.) Get a PAM048/050 from any dealers
2.) Get a A7750 pam date wheel
3.) reluming and date wheel transplant