Phil Ledgerwood sold chromed A posts on an exchange basis around 2009, but the finish didn't hold up over time so they were discontinued. The Allen bolts just need removing and apply your favourite "solution" whether that be Coppaslip, ceramic grease, vaseline or whatever. Then just watch closely for the merest hint of corrosion. The finish on those A posts varies. My 2005 has an almost Hammerite look, which may or may not be original. It hasn't shifted in 19 years. My 2016 has a sort of battleship grey semi gloss finish. It's still OK after seven years despite the worst Scotland could throw at it.
The point is this. If you pay over £70k for a car, corrosion of the A posts after such a short time isn't good enough.
I have found that
when it comes to corrosion, Nature always wins especially in humid places. It is easier to make metal-on-metal decisions using a Galvanic reaction table, which I have just
freshened up for you on gomog for you. Grease and miracle sprays only work for a time and when you find they have failed, rot will have irremediably spread especially in a damp climate as water is a rot catalyst. It is less hassle to go with nature gave us than fight it with face creams.

Same advice I give to my wife!

There are only two types of the subject bracketry that, IMHO, have been absolutely gorgeous and long lasting. The pre-1977 chromed bronze. These were followed by aluminum-sprayed bronze (a saving), then aluminum brackets which could be polished (sorta) and finally, upto a few years ago, the UK aftermarket offered polished stainless steel from John Worrall, (along with great ss Morgan fittings of all types). Though polished stainless is less lovely than chrome, it is bullet proof where chrome will eventually flake off and is fragile in impact. Lastly there is neoprene coated ...er...metal (the ultimate saving before plastic) [shiver])
But regardless what you have, you are always safe if you follow the Galvanic table and you are told the truth about the metals you put together. For example, for aluminum supports, use aluminum screws. I used chrome screws with my chromed ones and stainless steel screws with my stainless steel ones. I never had a single problem in this area with ANY of my mogs, be those in North American or the one I kept UK/Europe. Isn't that wotth waiting a couple of days. The cost is negligible considering the look and lack of rot risk.
I dislike carrying more than I have to when mogging.
Though you'd be surprised with what I do carry! Whatever the metal you need you can google to find it a fitting that matches it or the galvanic table laws. I favor the USA's Garner Westcott. (Being Canadian I have no patriotic conflict on where I buy parts as long as they are the most suited.) GW has the world's largest choice of fittings I have ever come across in chromed, graded, polished and Jw has retired. GW serves the collector automobile and motorcycle crowd.
https://www.gardner-westcott.com/
And here is a UK source selling aluminum. gmg