I have a few MOG related plates and a few non MOG personalised. All but two bought direct from DVLA website. One from the DVLA auction at the Morgan factory and one from a plate dealer.
The one I bought from a plate dealer was advertised at £18,000 but he auctioned it and I got it for £4k. Still a bit expensive for a bit of vanity (my US motorbikes have generally had vanity plates for the grand total of $25 a year!)
The bargains were probably the 2 MOG 3 wheeler plates at £250 each including EV03MOG for when it eventually goes into production :-)