Tales of the BatmanThe story you're thinking of Revil is called "Neutral Ground". About a shop owner named Kittlemeier who repairs and builds new costumes and gadgets for Batman and a few less reputable figures. One of the things I loved the most about this short story was that none of the clients are identified by name but by very distinct and obvious (to Batman readers) characteristics. This was also one of my favorite stories from the collection and is actually included as an excerpt in the Amazon listing.
This was a really great book. My dad used to read me one story each night before bed. I'd highly recommend it to anyone interested in some less conventional Batman stories. I also remember the other story Revil's talking about where Batman disguises himself as a nightclub comedian (I don't remember if he ever went onstage though) but it was a very cool example of one of Batman's many talents. Much like
Batman: The Animated Series, the short stories were excellent at showcasing the different abilities that Batman is a master of. I don't remember the other Joker story where he tries to get someone to kill themself but we may not have gotten to that story.
Here's a list of the stories contained and their authors:
Neutral Ground - Mike Resnick
Command Performance - Howard Goldsmith
Subway Jack - Joe R. Lansdale
Northwestward - Isaac Asimov
Museum Piece - Mike Resnick
Wise Men of Gotham - Edward Wellen
Robber's Roost - Max Allen Collins
Brothers in Crime - William F Nolan
Death of the Dreammaster - Robert Sheckley
On a Beautiful Summer's Day, He Was - Robert R. McCammon
The Joker's War - Robert Sheckley
Endangered Species - Greg Cox
Copycat - John Gregory Betancourt
A Harlot's Tears - Ed Gorman
Reformed - John Gregory Betancourt
Vulture: A Tale of the Penguin - Steve Rasnictem