were can i buy a tee for oil pressure gauge installation

I doubt you can find a tee in that configuration, so you will need to piece separate fittings together to get what you want. Take a look at McMaster.com if you have not already. That is where I got the BSPT fittings I needed in the past.

home depot or lowes may have something you can peice together. maybe local hardware store?

home depot won't have bspt only npt parts... i second mcmaster carr.. that's where i got my T from... check this post http://www.toyotanation.com/forum/t134386.html has the part# which was used to make it work for my car.. but sounds like u have the same problem as me