No. You cannot buy diplomatic passports. These are not for sale. For a few thousand you could buy a fake or fantasy one.
If you make a significant donation to a political party, then it is possible to get one. For this you need good political connections. There have been scandals in the past involving small countries in Caribbean, Africa where such passports are sold for large sum of money by corrupt officials to dubious business people to hide their tax money or to escape from prosecutions. Many countries officially maintain a list of who holds diplomatic passports.
It is important to note that diplomatic passports does not automatically come with immunity, a misunderstood perk. Immunity applies only to an accredited diplomat and then only within the receiving nation.There are several myths surrounding diplomatic passports.
Article 8 of Vienna convention explicitly mentions who can be appointed as diplomats. It clearly states non citizens cannot be issued one.
- Members of the diplomatic staff of the mission should in principle be of the nationality of the sending State.
- Members of the diplomatic staff of the mission may not be appointed from among persons having the nationality of the receiving State, except with the consent of that State which may be withdrawn at any time.
- The receiving State may reserve the same right with regard to nationals of a third State who are not also nationals of the sending State.