Affordable low-number tanning creame

I tried searching for "tanning cream" and got nothing. Then for "sun block" and got a bunch of into about a Troncones hotel.

Question: Where do you find the most economical low-number tanning cream or sun-block?

I don't ever see low number tanning cream these days anywhere, in fact. Mostly see only 30, 40 and 100. My 30 year old stash of 8 & 15 is finally running out and I'm going to have to break down and buy some. Thanks!