Good News for those still collecting, especially Australian fans, Season 5 - The Ninja Tribunal - Australian Version - Brand New, is available on ebay now.
http://www.ebay.com.au/itm/Teenage-Mutant-Ninja-Turtles-Collection-5-DVD-2007-3-Disc-Set-Rare-TMNT-/271589556260?pt=AU_DVDsBlurayDiscs&hash=item3f3bff c024
I'm also one who had the first 4 dvds set and kept putting off buying the rest of them till it was too late.
Well, I've been binging on the series recently catching up on all I missed (I'm up to Season 3 Episode 4 now) and thought what the hell I'll hunt them down. I was prepared for the long haul but to my surprise I have been really lucky with prices over here in Australia and have managed to find most seasons in full box sets (Except the Fast Forward Series which is 6 Separate DVDS but good enough) and I had to get the rest of Season 1 (The Raph 4 DVDs) from amazon but they were all less than $8 new each so all good there and All new so far....
Back to the Sewers might take some hunting...and patience. Can't find it anywhere except for a New Zealand site but not sure if it will ship over here or if they've updated their site on availability.
Hell, I'm actually excited about receiving them in the post and feel like a kid all over again. Counting down the days. I'll post up pics as soon as they arrive.