Yes MSL reader from the play store works for me.
This is a bit too late since you've activated already, but when you activate your phone online (boost.com that is) they actually give you your msl. Can't quite remember when in the activation process but there is a link few screen after entering your ESN. Every android phone I've activated, boost has provided the MSL.
Edit: The link sent me to a page with all my info on it
To be able to begin making and receiving calls, you must follow the instructions below.
1- Turn on your phone.
Your phone will display "Contacting Network"
After the network has been contacted, your phone will then display "Your device has been activated"
2- Press OK for the phone to restart and complete programming
3- If that didn't work than you need to use the account data and instruction below to manually program your phone
MSL: ******
MSID: **********
MDN: **********
##CLEAR# (##25327#)
To be able to begin making and receiving calls, you must follow the instructions below.
Turn on your phone.
The phone will go through various notifications during the activation process
NOTE: This is an automated process; you do not need to acknowledge these notifications.
After the network has been contacted, your phone will then display “ Your device has been activated”
Press OK
NOTE: If your device is not active after 4 hours, please call Boost Customer Care at 1-888-Boost-4U (1-888-266-7848)