malling wrote:Therefore I wanna know which pf from other manufactures I can use instead.
The Rancilio commercial portafilter certainly fits:
From the Buyer's Guide to the Elektra A3The OEM bottomless for E61 groups also fit ("Faema style"). You could take your portafilter to a machine shop, but keep in mind the bowl is tapered, so the hole will need to be smaller so as not to compromise the strength of the handle joint.
malling wrote:as I have understood it's not possible to use LM pf, but why is that. ??
The channel cut in the grouphead is too narrow to accommodate the thickness of the ears of the La Marzocco portafilter (i.e., it can't be engaged to lock in).