I mainly use Intellect 5 200 mAh/45C saddle packs as they also fit my TRF511. I do, however also have some GP 4300 mAh/35C stick packs that only fit the TRF201.
If you do not need saddle packs, get Intellect (IP) stick packs. If you have or plan on getting a saddle pack chassis, use only saddle packs for all your cars. Get the Intellects from a Hong Kong-based eBay seller and they will be hard to be for the price. Most IP-cells are EFRA-legal for racing.
If you want to make sure that what you buy, regardless of make, double check against the EFRA-lists here:
Stick packs:
http://news.efra.ws/fileadmin/docume...20V3%20pdf.pdf
Saddle packs:
http://news.efra.ws/fileadmin/docume...0pdf%20105.pdf