The pulse generator was also published in AN47 (Page 93). The whole app note from Jim Williams is a classic and worth to be read a few times
http://www.linear.com/docs/4138I build one a few years ago in a kind of split design similar to AN47. Mine has the 90 V power supply together with battery and on/off switch in a small plastic enclosure, and the transistor with BNC plug and the B, E, C resistors and capacitor in a separate tiny tin enclosure. Between them 1 m of cable to connect the power. This gives me a small separate head, not much larger than the BNC plug.
The power supply is build on a strip board, and - sorry Linear - I substituted the LT1073 with another boost converter IC I just happened to have in the drawer.
The "head" is build similar to what Jim Williams shows in AN47, although I didn't use a second BNC connector to connect the power. To keep the head small the cable is fixed attached to the head in my version.
If you have the parts, this is a weekend project. Just be careful, if you mess up the power supply you can easily get more then the desired 90 V out of it, and 90 V is already beyond ELV, so officially in the "it can kill you" range.