I'm pushing a 48x15 at the moment but find it just too big, i'm going to try a 17t Surly sprocket on the back instead.
Do you favor changing the sprocket or the chainring to increase/decrease gear size?
Change the sprocket it'll be a lot easier and a 48T chainset is pretty standard. I don't think you'll go far wrong with a 17 tooth rear sprocket, plus larger sprockets are supposed to lessen chain wear… not that you get much of that on a singlespeed anyway.
This here Giant came with 48/17 as standard. Works well for an unfit me.