Do you want to keep the same use year? If you don't mind a different one, The Timeshare Store has two 150 point contracts listed on their website. Use years are August and December and you might get the points more quickly than if you wait for Disney.
By the way, I don't work for TSS, but DH and I recently purchased an additional contract for BWV through them. The process couldn't have been any easier and everything went so smoothly. We tried to purchase points through Disney in March and it was such a hassle - we couldn't get a straight answer from anyone at
DVC, they said some people were on the waitlist for over 6 months because additional points at BWV were "very rare" for our use year (December) and wouldn't we rather buy points at SSR?, etc.
We researched additional contracts at TSS, made an offer and closed on the contract in about 2 months. If we ever decide to do it again, we'll definitely go right to TSS.
Good luck!!