I think someone here got something signed at Bridport. That, of course, was a much more low key sort of event than a concert - small audience - small venue - a little local affair, really. Maybe that's the sort of thing to look out for.
The other possibility, if you're in the Netherlands, is to try leaving something with the local promoter - maybe not the main man (woman?), who might feel it a bit beneath them to ask, but somebody else at the office, like the boss's assistant.
In theatres where a play or show is running for an extended period, you can sometimes get an autograph simply by leaving a spare programme (book) for the show with the meber of staff at the stage door. Where MK is playing a show several nights running at the same venue, this may be a possibility. However, the RAH now has a low level car park for performers etc, enabling them to avoid leaving through the stage door.
A year or so ago, we saw Dame Judi Dench in a stage play in London. After the performance, the staff at the theatre set up some barriers in the street in front of the theatre, asked everyone waiting there to get behind the barriers and then she came out and signed everything presented to her and had her photo taken many, many times. Some of the young folk there had flown from the Far East to see her live. Such is the power of James Bond, I guess. Anyway, I was much taken with her preparedness, willingness even, to do this but I'm afraid that younger performers (and MK is younger than she) lack that kind of attitude about the relationship with their audience.
I don't know whether PCM would be prepared to help. Somehow, I doubt it, but it might work, particularly if there is a special reason behind it. A few years back, I contacted someone's agent with a request for an autograph to mark a special occasion. I explained what the occasion was and the reason why the autograph would mean so much. I was then put in touch with that person's PA, went through the whole thing again and got the autograph I sought.
One problem nowadays is that artists feel that autographing something is just as likely to be for someone to sell on eBay as for a personal memento. In other words, someone is asking just to make a profit. These days, autographs are being replaced by "selfies", they say, but maybe that's one of the attractions - a selfie is more likely to appear on Facebook than be auctioned off to the highest bidder.
