In the UK myself, (no, I don't know and haven't located any supplier) I'd be very cautious about anyone who contacts you in response to a plea for an SN source. In general the few UK members who manage to obtain SN seem to treasure the supplier's particulars like gold dust, and are most unlikely to just pass it on indiscriminately to a complete stranger who has only very recently been accepted onto the group, my view.
My own experience is that genuine UK producers/suppliers will only sell to recognised and registered businesses or labs and delivery will be to their commercial premises.
SN is also on the Customs & Excise watch list for imported chemicals, so if ordered from overseas the sender will need to give an inaccurate description of contents.
Sorry if this all sounds very discouraging … it's just as much of a downer to me.