. I've never measured the seat, so I'm not sure what size it is.

I've just looked up the size of the Selle SMP TRK and it's quoted at 272 x 177. It is wider on the sit bone area than the male equivalent, my husband has one on his bike too. Don't know how much they would be there but they are the about the equivalent of $45 ish here.
The Lycra will get you :-)