Im relatively new to all of this and what not but isint the new Portra 400 very very similar to the 500T your all trying to get. You can see some comparisons of them here, both in terms of colour and low light. I understand the colour balance is different but surely thats an easier fix then cutting down huge rolls of cine film and finding a specialist lab, filter over the lens maybe? quick photoshop layer for those who scan.
comparison by twinlenslife --- http://www.twinlenslife.com/search/label/Editorial