The subject recently came up in my missions group and one of the players would like to explore the possibility of getting a ally spirit.

At first I thought they weren't allowed but my google-fu turned up a response from Bull confirming that they were indeed allowed. However there is one complication, you need a formula for the spirit. Now you are not allowed to "craft" stuff in missions so that would indicate that you can't make the formula. However you can get the formula by going on a metaplanar quest. Now I am not sure if metaplanar quests are allowed in missions or not or how long they would take if they are. The book also points out that an initiate can locate a formula that matches her needs.

The way I would tackle this in a home game if I didn't want to play out the metaplanar quest would be to simply allow the player to go on the quest, find the formula and write it down and have him cut one week of his lifestyle. This is assuming he has already initiated at least once. This could also be grabbed as part of an initiation.

So my question is simple, how do players go about getting the formula for a allied spirit in missions? (I realise the answer may not be as simple as the question)