Hi Azakaria

If the school you are desirous of joining is asking for 2 professional recommendation letters , you can ask your manager and one of your colleagues to write a letter each. Just in case you are not able to get a recommendation letter from your colleague , you can request a professor of previous undergraduate education. If you know any organization where you could give a 7 days voluntary work and earn a certificate or recommendation that would serve the purpose as well.

Thanks

One recommendation from your manager can be given to all the schools.

Careful with this, though, since some business schools ask for specific issues to be addressed in recommendation letters.

For example, Columbia tends to ask recommenders to detail feedback that they have given to recommendees. And Haas asks how a recommendee lines up with the school's guiding principles.

It might not be ideal, but you'll need to ask your recommender to specifically address each school's requirements.

However, if, like you say, that the schools you are looking at do not ask for a "specific form," then this is no problem. Just make sure this is actually the case.