Nice, I am not familiar with that catalog.
As for Higgins & Gage, it has been out of print for decades now.
I believe the last revision was some time in the 1980's, while the sections that I have range from the 60's to the mid-70's (with various erratas & addendum).
You may be fortunate enough to find sections on
ebay, but be weary they can be quite costly to acquire now.
When I acquired the sections that I do have (1-10, 15, & 17) I waited till they were auctioned as full sections and not just photocopies (but actual originals).
You will come across those that are selling piecemeal by country (that is the extremely expensive route).
Currently the entirety of Section 9 Iceland to Ivory Coast is up for auction on
ebay - see
http://www.ebay.com/itm/Higgins-Gag...AOSwll1Wu2qgHowever, if you are solely interested in European Postal Stationery then Michel would be your best bet.
But that is up to you.
Regards,
Stampalotapus