There you go SB an explanation of Pre and Post nominal letters, and may be the OP can work out what letters to use, like ********.
Post-nominal letters, also called post-nominal initials, post-nominal titles or designatory letters, are letters placed after the name of a person to indicate that the individual holds a position, educational degree, accreditation, office, or honour. An individual may use several different sets of post-nominal letters. The order in which these are listed after a name is based on the order of precedence and category of the order. Post-nominal letters are one of the main types of name suffix.
Change your name to Raving Nosh so when asked for name and initials you can say, in a loud proud voice, I'm Dungbutton RN. It worked for a bloke whose surname was Albert, they even made a film about him!!