5" templates are not commonly available, to my knowledge.
The sashing size will depend upon your block size. My DD, and art major, has suggested a multiple of the block size to maintain proportion. 1.5" (2" cut size) would be 1/2 of a 3", or 1/4 of a 6" block.
If your block is 5" finished, I think the 1" finished size sashing would be good. Sorry I can't tell you where to find a 1.5" wide ruler. I haven't seen them. Perhaps someone else will know where to look.
Good luck finding one!