The Pioneer A06 and the Sony ???? are the only two -R and +R burners available. Rumor has it that Apple is now using the Sony mechanism for their new computers and there is no software available to burn +R disks on the MAC (unless Toast 6 can do it now)
I have an EZQuest A05 Firewire external that works really well and I can recommend EZQuest if they have the A06 mechanism.
Check out www.macsales.com for great prices on EZQuest products.