Well, I finally grabbed it in my most recent order. I can tell immediately why it wasn't scanned back with the main book from C91. But hey, I care more about posterity than if the book is actually quality fapping content. With this, all Udonko extra booklets should be available on E-H/Ex, not much more Udon-Ya content to upload, but hopefully sensei doesn't get mad at me like Pochi did.

As always, you can get the full HQ raws at the MEGA link below. I only scanned them at 600 DPI this time, I don't figure anyone will jump at the chance to finish the job on this one. Though this gallery has light leveling on the pages, the MEGA link has the TIF files with the Levels Adjustment layer that can be removed.
https://mega.nz/file/yXYCCZxA#aTe9s_z-ejBsgAueIuV-PlQ-3qiVtT5_q-GfV8XFcnc

Again, as always, I don't take requests, I don't have a website either.

@ Shilu, is there any other stuff I haven't gotten aside from weird things like the L and R zenshuu/tankoubon?

https://www.doujinshi.org/book/1133504/UDONKO-15/

Base +61, gradius +6