Other then bristol, what is your smoothest paper that is suitable for pen and ink that does not bleed or have too much absorption? I am looking for something around 250 GSM or higher.

Saunders Waterford Hot Press is the smoothest paper we offer that is suitable for pen & ink. This paper comes in a 140#/300gsm weight in 22x30 and is offered in white and high white. The external sizing for water media prevents bleed when using pen and ink.

Another paper this is ideal for Pen & Ink is Stonehenge. This paper, however, has a slight vellum texture and may be too rough for what you are looking for.

Another great paper to look at for Pen & Ink is Yupo. It's super-smooth like ice, but know that it's a synthetic paper so you'll need to use permanent markers and pens.