Timo, and group ...
Here in Toronto, I had a similar problem locating a supplier of AeroShell-33, for my AP-900, and even SHELL OIL Corp. would NOT sell it to me unless I bought a large quantity, perhaps a shipping palette full of them. They couldn’t figure out why a private individual would need it.
However, I eventually discovered that I could simply drop by an “Aircraft Maintenance Supply” business, near the local major airport, and buy just one calking/greasing gun tube of it over the counter. That’s enough for a lifetime supply for 20 or more scope mounts ! The dealer even wrote the “adjusted” expiry date on the tube he had on his shelf stock supply, normally provided to aircraft companies mechanics – since government safety regulations require that aircraft landing grease they use, like this, must NOT be older than 4 years since production. The grease components begin to separate somewhat from its oil base, if it is older.
So, I suggest you check a nearby airport, even a small one, for aircraft maintenance suppliers, rather than going through the hoops of locating some specialty company, who would sell you some – and their grease supply might even be out-dated - while a major supplier would have fresher grease, with their constant stock turnover. Besides, being a volatile fuel product, it might be banned from quickly shipping to you by air.