Hi and welcome to the forum.
You can check out the bikes for sale in the classified section top of this page.
Some guesthouses have a noticeboard on which travelers post bikes for sale.
There are also grocery shops around where they allow expats to place a card in their windows with things to sell.
If you are wandering around LP and spot an expat on a bike, maybe approach them for information.
There are motorbike rental places in LP.
