I might be wrong ( wouldn't be the first time.) But I seem to remember that, when I needed a 3/16" tee with a hole for mounting on my frame, I walked down the block to the Napa store.

Otherwise, I know the usual racing places have them:

http://www.summitracing.com/parts/ear-972050erl
http://www.summitracing.com/parts/gar-j9034
http://www.jegs.com/i/JEGS-Performance-Products/555/63080/10002/-1?parentProductId=1403915
http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?No=0&Ne=1 2 3 13 1147708 1500000+1500000&Ntt=inverted+tee&Ntk=all&langId=-1&storeId=10001&Jnar=0&N=0&catalogId=10002&Nty=0

I certainly won't pay the high price the racing places ask for so I use them mostly for manufacturer make and part numbers so my FLAPS can interchange for me. Those racing places get enough of my money.

Mark

1951 Chevy Suburban
In the Stovebolt Gallery
Lots and LOTS of pictures
Project Journal --- 10 pages worth!