A dual mass flywheel can be skimmed if the spring tension is still in spec...you just need to find a place that will do it for you.
If you convert to single mass you will need to find a sprung hub clutch disc that will fit on your gearbox input shaft (even more so seeing as you are worried how the car will be in traffic)
And 6k to me feel on the expensive side for a flywheel.
You will also get a lot more gearbox chatter with a single mass, which is something else to consider if you will be driving in traffic.