Unless you have a big CTR Flash Card, you have no other choice than pressing B.
I'd say, ask Game Developers for one of these, 5 years later?
After getting the CTR Flash Card (with game), you should be able to use the DevMenu.
Note: Nintendo's Flash Cards are about the same size as a Retail Cartridge, while the ones 3rd Party Developers use, have an extra bulb on it.
The ones from Nintendo, can be directly booted without going to the DevMenu first, the ones from the 3rd Party Developers, can only be booted from the DevMenu.