Finuge pay no attention to all these limp wristed tackle tarts with their airy fairy light weight piddly little short modern rods. What would any of them do if they went back to the days of glass fibre let alone cane! You don't need to eat spinnage to use a 12' single hander
That said there aren't many options for a 12' single hander, it might be worth hunting around for something second hand.
I have a #8/9 12' Diawa sea trout special from some years ago, it is fine as a spate river salmon rod but way to stiff for sea trout. I also have a 12' Hardy blank bulit as a single hander but this, like many older Hardys, is very soft.
Enigma/Fishtec used to do a #7 12' single hander.
Marcus Warwick (not sure he is still trading, last seen in Axminster) used to sell the Charles Mclaren 12' sea trout rod either in a #5 or #7.
Get googling
Andy