Joined up especially to reply to this.
I haven't heard of a buy back type thing being done here.
But there's the website Trademe (kinda like ebay), where people advertise bikes and cars and what not for sale. So you could probably organize to purchase a bike where ever you arrive to and then list it again, could always sell it a bit cheaper for a quick sale. But id you have family over here leave it at there place while it sells.