I press mostly foliage and use phone books. But try www.herbariumsupply.com for blotting paper...some prefer it for flowers in particular. For archival (acid-free) supplies of matboard, mounting paper, etc. try Dick Blick. josh

Here is a link that might be useful: Dick Blick

For drying I use regular blotters that are made for standard plant press or very thick paper from the art store with high rag content.
For mounting I use acid free paper. It's relatively cheap at the paper stores (here it's ExPedX-the "old" Dixon paper store). I paid under 15 dollars for 250 sheets of recycled and acid free, heavy cover stock. They also sell justt about everything they have by the sheet (10-20 cents each) for smaller projects.