Richard.
Just a warning about the older Tamiya Kits. The teeth on the drive sprockets can be way too wide to fit some indy Tracks, and sometimes they are spaced too wide as well. Be prepared to undergo some surgery. Which flakpanzer are you building? Wirbelwind, Mobilewagon (quad 20mm), Mobilewagon (3.7mm), etc.
If you are in the USA, check out the Panzer IV Group build in this forum. Some guys are replacing their vehicles tracks with After market ones, and if you ask real nice, maybe someone will post/sell you cheap their old ones. Maybe one of the guys using Fruil will cough up their DML indies for you. You have nothing to lose by asking.
PS. The falkpanzers mostly had the late pattern 40cm tracks with the ice cleats. The early panzer IV's had 36cm tracks, whilst mid pro vehicles had 40cm tracks without the cleats. In other words, an Ausf D's tracks are no good to you.