You can offer bounties of 50,100,150,200,250,300,350,400,450 or 500 reputation. A user with 5k rep who is unwilling to spare even 1% of their reputation to get their own answer noticed is unlikely to engender much sympathy. How would you ask for this? By leaving a comment along the lines of this?
I really need an answer but I'm not willing to part with any of my thousands of Useless Internet Points®, can someone else please offer a bounty for me?
I might understand this from someone who has very little rep but from a >5k user!? That said, you can always ask someone you know in chat but I doubt that a user of your reputation begging for one will be well received by strangers. There is no explicit rule against it that I am aware of, I just think it is much likelier to backfire than to work.
Imagine someone begging for coins while playing with their 500$ smartphone. Would you consider giving them money?