Thanks to Crowd Supply, you can now buy the LiFePO4wered/Pi+ on Mouser! :)  They seem to be selling well and stock is getting low, so if it's more convenient for you to order there, you might want to get one soon before they run out.

I just shipped more stock to Crowd Supply so this may be refilled soon, but since all of this is handled internally between Crowd Supply and Mouser I have no visibility on when that might happen.