This old super smooth original HP plotter paper is still relatively easy to find on eBay. We use these sheets when we need a really nice smooth surface to plot on without excessive bleed. They are available in A and B sizes/US Ledger and we recently acquired A3 size. This size came in a larger box containing 250 sheets, instead of the 50 sheets bundled in B-size (11 x 17″) that we already had.

The box also includes a nicely designed instruction sheet with best practices. Here is a scan for you fellow enthusiasts to enjoy as well.

Also in PDF here.