A friend gave me a light that takes BR435 batteries. Came here to find a source and didn't. So after Google and EBay, I found maxmax.com. They have the batteries for $2! The best price I could find for a few cells especially. However they use UPS only and ordering 6 batteries made my total over $26.
It looks to me like some of their lights are StreamLight models though I didn't see any attribution to SL. My thoughts are to call and ask if the can ship in a padded envelope or cardboard sleeve by USPS for less. Wondering if I should try or look elsewhere. They have some nice looking BR435 lights.
I did search both CPF and MP and found one older post, not bad but not current.
They do have some interesting pages on their site. This one is safe, but perplexing