What alternatives exist for finding and appointing an executor for one's will/estate for a person with no close family or qualified friend? Are there pros and cons?
Often one chooses your accountant, your financial advisor, or your lawyer. Another option is to appoint the trust department of a bank.
I personally, as a lawyer, have a policy of not consenting to do that except in rare cases like the one in this question, of a client who just doesn't have anyone and has an estate sufficiently small that a bank trust department would not be cost effective or well suited to handling some aspect of the executorship. But, I have done it a few times in those cases. Most lawyers I know of take a similar position.
If no executor is designated, your estate will usually be administered either by a large unpaid creditor, or by the public administrator (whose job is primarily to administer estates in cases where there are no next of kin, no executor has been designated, and there are no unpaid creditors who have stepped up to do the job).
Age UK, a British charity that supports people who are elderly, have this to say on the subject:
If you don’t have anyone that you feel would be suitable, or your family and friends don’t want to take on the role, you could appoint a professional executor, such as a solicitor or an accountant.
They also offer the following pro and con.
This can be especially useful if your estate is particularly large or complicated. A professional executor will charge for their services and this will be paid for out of your estate.