Blotting paper used to be available at every stationary store.
Good luck finding one since Staples and the like took over the
market.  I have also looked at paper supply stores, etc., and was
not able to find blotter paper.

A few years ago I bought a package at a military surplus supply.
This stuff is Army green as it was used on Army desks.  The little
package was a full ream, 500 sheets of 20" by 30" or so paper and
I still have most of it.  I will send it (cut to fit in an envelope)
to anyone who needs some.  I will not be where the paper stored
until April.

Best regards,
Spencer Chase
http://www.spencerserolls.com/