Any (good) local bike shop should carry a range of seatposts. I'd imagine it'll be 27.2 diammeter, but then Raleigh did tend to use different sizes every now again. A local bike shop should have a set of calipers to measure the diammeter (if you don't have any). Saddle clamps are pretty standard, so you shouldn't have issues getting a saddle to fit the post.
Any (good) local bike shop should carry a range of seatposts. I'd imagine it'll be 27.2 diammeter, but then Raleigh did tend to use different sizes every now again. A local bike shop should have a set of calipers to measure the diammeter (if you don't have any). Saddle clamps are pretty standard, so you shouldn't have issues getting a saddle to fit the post.