You can only rent 50% of the points required for the transaction, so no, you could not rent the entire 9000 pts.
I haven’t seen too many ads related to “selling” RCI Points, though I did find one listing several months ago on RedWeek. Any “sales” need to be handled discreetly, since RCI probably prohibits the actual “selling” of points.
If you need to obtain the 9000 points a PFD might work out for the best, since that transaction should be able to be handled quickly by RCI, and you have the excess for more 9000 pt vacations.
Also if your TS is a lock-off you can consider doing a PFD for one portion of the unit, or you can do a separate PFD for each portion of the unit and get more points that one PFD for a combined unit, though you will have two PFD fees.
Finally, check the Last Call Vacations, many times the same resorts are offered for both Last Call and the 9000 point last-minute deals.