For anyone interested,
I recently came across Ridata DL-R (4X speed) discs here in Toronto at PC4U computers (Spadina just south of College on the east side) and at APlus computers (on College west of Spadina on the north side).
PC4U sold me their last disc ($4.00 each or $19.99 for a 5 pack). The sales lady told me they'd be ordering more.
Aplus computers had a bunch of 5 packs at $29.99 (not as cheap as PC4U - but hey, if you're really desperate)!
I haven't tried to burn anything yet; but, I'm hoping it'll work fine in my older player.
MacPro - 8 Core 2.8 Ghz / 16 GB RAM / Nvidia 8800 GT 512 MB / Snow Leopard