You're probably not going to get a specific appointment for something so small. Inking time will be less than 1 minute. Total time in front of the tattooist will probably be less than 10 minutes. Be prepared to pay a shop minimum (which will vary depending on which shop in Boston, but probably $75-100).
I'm not familiar with the shops there, but the pitfall is that it takes almost nothing to screw up very simple design like this, so you don't want to end up in the hands of some newbie apprentice or an experienced person who isn't really invested or interested in helping you out. It's going to be a balancing act.
2nd on @Dan's comment regarding the white ink choice